The 8 Best Long Underwear for Women of 2024 | Tested

Our team has tested over 50 pairs of the best long underwear for women over the last eight years, including the top 22 in our latest review. Each next-to-skin layer has seen loads of sweaty missions, from backcountry splitboarding to multi-pitch rock climbs to ultra trail runs — all in pursuit of finding the warmest, most breathable, and most comfortable pair of bottoms available. We test across North America throughout the colder half of the year, from the sandstone deserts of Utah to the high mountains of Alaska and California. After comparing these products side-by-side, our comprehensive review offers product insight and expert recommendations to help you find the perfect pair for your next winter adventure.

If you're looking for more lower-body layering options, we've also tested the best women's travel underwear and the most popular hiking pants. For your upper body, we've reviewed the top-rated sports bras, the best women's base layer tops, and best fleece jackets for women.

Editor's Note: We updated this review on May 3, 2024, to include three new products and one new award winner.

The Icebreaker 200 ZoneKnit Merino Leggings offer exceptional performance within a 100% Merino wool design. A tightly woven, 200 g/m² fabric and body-mapped ventilation panels in specific locations help these bottoms insulate while effectively releasing sweat generated during high-output cold weather sports. Ultra-fine 18.9-micron fibers and a flattering, high-waisted, and slim fit allowed our testing team to stay comfortable all day. And speaking of comfort, features like the gusseted crotch increase the range of motion, while the flatlock seams are thoughtfully placed to avoid distraction or discomfort from chafing.

Though we experienced no issues with durability during our Spring testing period, it is worth mentioning that we have tested several iterations of these bottoms and know that the perforated ventilation panels can often be the first location where the fabric will fail. The perforated ventilation panels cover nearly half of these bottoms, and we remain weary of the longevity of these expensive bottoms. If long-term durability is a top concern, we suggest the similarly designed SmartWool Intraknit Thermal Merino Bottoms. However, be prepared for a much more rigid and thicker construction that doesn't offer the same amount of comfort or freedom of movement. But for what it's worth, the latest update of the Zoneknit gives us confidence that these bottoms are more durable than ever. If you're interested in a highly breathable design that enhances both the odor-resistance and wicking capabilities of 100% Merino wool, the 200 ZoneKnit offers high performance with a unique, modern, and stylish design that can't be beaten. Or, if you like the sound of the 200 ZoneKnit but are after a long underwear bottom made of thicker fabric, we've also tested the midweight version, the Icebreaker 260 ZoneKnit Merino Leggings. The 260 ZoneKnit is identical to the 200 ZoneKnit, with a little extra thickness in the upper thigh for additional warmth during the coldest months of the year. Ultimately, we selected the 200 ZoneKnit as our Merino wool favorite based on their lighter-weight fabric, which we believed offered a more versatile, year-round performance.

Read more: Icebreaker 200 ZoneKnit Merino Leggings review

Known for its amazing wicking power and breathability, the Patagonia Capilene Thermal Weight rises to the top for synthetic performance. Constructed of 92% recycled polyester and 8% spandex, this pant (though marketed as a thermal weight) has more of a midweight construction that provides optimal performance throughout the year. The see-through design allows air to penetrate the fabric, making the subsequent wicking power hard to beat. While synthetics aren't typically known for their next-to-skin comfort, we love how the Polartec power grid fleece feels against the skin and its stretchy fit that moves with our body.

Unfortunately, despite the HeiQ Fresh odor control treatment, these bottoms get smelly after only a few days of use, so we can't recommend them as our first choice for multi-day backcountry missions. The Capilene Thermal is admittedly a bit more niche — they aren't your “hang around at camp lounge pants.” However, they dry quickly, excelling at technical, high-output pursuits. If you seek a highly breathable synthetic pair of long underwear that doesn't skimp on comfort and fit, these will not disappoint. We also like Patagonia's Capilene Midweight Bottoms for a lighter weight, more affordable, and much more durable alternative, but we note they're not quite as warm, breathable, or quite as comfy as the Capilene Thermal Weight.

Read more: Patagonia Capilene Thermal Weight review

If you've been wanting a Merino base layer but cringe at the average price tag, consider the competitively-priced Minus33 Franconia Midweight Wool Bottoms. These midweight leggings are constructed from 235 g/m² 100% Australian Merino Wool, providing super soft comfort next to your skin. Thanks to the tightly woven fabric, they are also in the running for some of the warmest bottoms we've ever tested. And while they do not feature fancy ventilation panels or perforated fabric, the ultra-fine, 18.5-micron Merino wool naturally thermoregulates your body temperatures, and the looser fit allows more air to permeate the fabric and wick sweat away from the body.

The Franconia Midweight is true to size but features a looser fit, so we recommend sizing down if you prefer a more athletic, slim-fitting bottom. And while we love the super soft Merino wool, we couldn't help but notice how easily these bottoms can stretch out and lose their structure, loosening them up in use. But don't worry; their structure can be restored with one wash cycle in a machine. It is also worth mentioning that even with all this stretching potential, the thin and low-profile elastic waistband effectively holds these bottoms in place, whether worn on their own or beneath your ski bibs. Overall, we were impressed with the durability of these Merino wool bottoms and believe they offer a ton of value in exchange for a more modest price tag.

Read more: Minus33 Franconia Midweight Wool Bottom review

The REI Co-op Midweight Tights offer great synthetic performance at an affordable price. The blended polyester and spandex fabric feels incredibly soft against the skin and features a four-way stretch, allowing a full range of motion. While more of a lightweight fabric, these tights offer ample warmth for the shoulder seasons. When paired with thicker insulating layers, they are also ideal for the colder months of the year. These tights are a great choice for numerous cold-weather activities, featuring a fit that's true to size and durable flatlock seams.

Unfortunately, we were not impressed by the garment's ability to release moisture from the fabric after some high-intensity activities. While these tights wicked sweat away from our skin, they pooled near the waistband and took longer to dry behind the knees. We also noticed that the fabric retained odor almost immediately after our testing period began, and we couldn't find any mention of an odor control treatment such as other top-performing synthetic bottoms. All complaints aside, these synthetic tights impressed our testers with a competitive performance and a favorable fit, especially considering the modest price tag. We also tested REI's Lightweight version of this pant, which are even more affordable and dry quickly. Still, they're slightly less warm and lack the same durability as the thicker midweight design.

Read more: REI Co-op Midweight Tights review

The Baleaf Fleece Lined Thermal is a highly affordable bottom that favors the design of a modern yoga or workout tight moreso than what you would typically expect from a traditional long underwear bottom. The synthetic polyester and spandex construction offers a fleece-lined interior for comfort next to your skin, and the thickness of a midweight construction supplies additional warmth. The spandex fabric allows the bottoms to offer a bit of stretch and a full range of motion, whether you're out for a trail run or holding your favorite yoga asana. The design also features three pockets, two of which run along the exterior of each thigh and are big enough for a smartphone or energy bar, and one more discreet pocket along the waistband big enough for a car key. The design is easy to layer thanks to a snug fit that is true to size and the high waistband, which allows other layers to fasten at your natural waistline. We love these tights for rock climbing as the harness easily layers below the thick, high waistband.

We really put these bottoms through the wringer during our spring testing period. We took them out for trail runs amongst the sharp and unforgiving plant life that lines the desert floor, wore them rock climbing in the very physical Indian Creek splitter cracks, and layered them below our ski bibs for spring backcountry tours in the High Sierra. After all that use and abuse, we noted some piling along the thick flatlock seams and one small hole (that didn't grow larger) on the exterior knee after snagging on a sharp sagebrush plant during one of our trail runs. Needless to say, our testing team was impressed with this highly affordable bottom that far exceeded its modest price tag. The comfortable, breathable modern design features a flattering yet functional fit that withstood all durability tests without retaining any odor in its synthetic fibers. Though not a traditional long underwear bottom for optimizing layered warmth in cold weather, these midnight bottoms offer a ton of versatility and are available for a very affordable price.

Read more: Baleaf Fleece Lined Thermal review

The Arc'teryx Rho Bottom is a super light, versatile, and high-performing long underwear bottom that features some of the most comfortable, internally brushed synthetic fabric we experienced in our lineup, along with a great fit. We love the high-rise, thick waistband that is not only flattering but functional, in addition to the slim fit that aids in offloading moisture from the minimalist design. These were some of the only bottoms we tested that feature a stash pocket on the thigh, which is great for storing energy gels, a couple of keys, or a phone.

This versatile design provides enough warmth and modesty for trail runs in the spring and fall or when layered beneath your favorite ski bibs for added insulation throughout the winter. The Rho is a bit pricey compared to other lightweight synthetic options in this review and should be weighed against the REI Co-op Midweight Tights if you're shopping on a tighter budget. The merrow stitching on the Rho Bottoms — similar to a welded seam — gets fuzzy when encountering velcro or a lot of friction from additional layers. Still, the Rho is high-performing and highly versatile, the perfect layer for running, skiing, or yoga.

Read more: Arc'teryx Rho Bottom

The SmartWool Intraknit Thermal Merino Bottom quickly became our favorite pair of blended long underwear bottoms geared to optimize cold weather performance. The fabric blend takes advantage of Merino's odor-free benefits and the durability of polyester. But what sets these bottoms apart is their gender-specific pattern articulation and unique ventilation panels that increase breathability throughout the design while capturing warmth generated during activity.

While we are truly impressed by the ability of the Intraknit to keep us warm when moving in frigid temperatures, this design is not without some caveats. The overall thicker fabric not only increases bulk when layering but also reduces the drying speed. And while we love the 2" waistband for the way it hugs our curves and keeps these bottoms in place, the waistband was typically the only portion of these bottoms that would trap moisture. Those things aside, this is the layer for you if you're looking for long underwear bottoms with a more substantial and warmer weight that still perform well during high-output cold weather activities. If you're seeking a wool pair to wear skiing that won't interfere with your ski boots, we recommend the Ortovox 185 Rock'N'Wool Short Pants.

Read more: SmartWool Intraknit Thermal Merino Bottom

The Patagonia Capilene Midweight Bottoms is a consistent and reliable long underwear bottom, offering excellence in durability and overall workhorse performance season after season. Thanks to their 100% Recycled polyester construction that features flatlock seams and a gusseted crotch, these bottoms are built to go the distance. The hollow-core yarns and the diamond-grid patterning help these bottoms to thermoregulate effectively by trapping warm air, wicking sweat away from the skin, and releasing it through the fabric. They're essentially designed to keep you cool when it's hot and warm when it's cold. We love that they are solid enough to be worn as stand-alone leggings and thin enough to be layered below your ski bibs for additional warmth in the winter.

We're proud to report that even after multiple years of testing, we've experienced no durability issues with these bottoms. In fact, they've outlasted almost every other synthetic bottom that we've tested over the years. The flatlock seams and tightly woven diamond grid pattern synthetic fabric are still going strong, even though we've worn them rock climbing and trail running in the desert that surrounds the Eastern Sierras. The Patagonia Capilene Midweight Bottoms are a great option for those seeking to maximize their investment for multiple years of use, and they are available at a fair price. The REI Midweight Tights are another affordable option worth considering — though they're nowhere near as durable.

Read more: Patagonia Capilene Midweight Bottoms - Women's review

When testing women's long underwear, we consider how each bottom can be useful. We take stock of what's on the market, selecting the highest-rated products with the best reputation. Then, we buy each layer at retail price and test them side-by-side for months at a time.

We've spent the last six years searching for the best pair of long underwear bottoms, which allowed us to record our experiences throughout all the possible cold weather conditions. We've taken each model on international trips and used each locally while climbing, biking, and exploring Colorado's San Juan Mountains and California's Sierras. After our field tests, we evaluate each product, score it, and share our findings and thoughts.

This review is spearheaded by Trish Matheny. After spending a very cold decade in the Tetons, she knows what she's looking for in long underwear performance. An avid rock climber, trail runner, and born-again splitboarder, Trish wears base layers almost daily when pursuing her passions amongst the elements in the Eastern Sierra. She hopes that by sharing her experiences, she can offer thoughtful recommendations to help you select the best layer for your backcountry adventures. Outdoor educator and avid adventurer Amber King laid the foundation of this review. She regularly opts for a pair of base layer bottoms when climbing, snowboarding, hiking, sailing, and trail running. As a result, she's stayed warm and comfortable in her travels, ranging from the Faroe Islands to the Cordillera Huayhuash of Peru.

A solid long underwear bottom is a key part of any outdoor wardrobe. Designed to sit next to the skin, it should wick away moisture to keep your skin warm and dry. While each bottom could be used on its own in warm weather, a base layer is typically used as part of a layering system during the year's colder months. To find the best pair for different activities, we look at a range of base layer bottoms in various weights, from light to heavyweight.

There are many great options out there that won't cost you an arm and a leg. When considering value, it's important to consider both performance and durability. The Ridge Merino Aspect is constructed from primarily Merino wool and boasts an affordable price tag relative to most competitors. Our testers were impressed by the flattering and functional fit, comfort next to the skin, and increased durability offered by the blended fabric of these affordable and stylish leggings. For just a few dollars more, the 100% Merino wool design of the Minus33 Franconia offers plush comfort and substantial warmth at a fraction of the cost of its popular wool competitors.

When it comes to value, the Patagonia Capilene Midweight Bottoms rise to the top of our list. They are followed closely by the impressive performance of the REI Co-op Midweight, which is especially notable considering it has one of the lowest price tags in this entire review. However, both are constructed from synthetic materials and are typically not as warm and cozy as Merino wool.

Our testers love it when an inexpensive bottom outperforms its price tag, and this is precisely what happened with the Baleaf Fleece Lined Thermal bottom. This synthetic bottom favors the modern design of a yoga tight or workout bottom rather than a traditional pair of long underwear that prioritizes warmth. We were impressed with the high value offered in this versatile three-season bottom that supplies fleece-lined comfort and a great fit that offers easy layering and enough durability to wear as a stand-alone bottom.

The insulative warmth of a base layer bottom balances with breathability to provide great thermoregulation. When evaluating warmth, you should consider that most models are available in various weights. The higher the fabric weight, the warmer it is supposed to be. However, we've encountered plenty of layers that claim to be one weight and perform more like another. To help you navigate confusing marketing claims, we provide side-by-side comparisons and let you know our opinion regarding the effective fabric weight each pair of long underwear bottoms offers.

During our testing period, we began by observing the fabrics and their construction, assessing the tightness and relative thickness of the weave. Then, we test warmth by playing and working in cold, inclement weather before sleeping in each pair under the stars on frosty nights. We carry our base layers on our adventures, cycling each pair in and out of use to see which offers the best insulation and warmth as a stand-alone piece or when worn underneath a pair of pants. We record our experiences, compare notes, and report back to you.

Through extensive testing, we learned that the natural organic fibers of Merino wool not only feel amazing against the skin but typically offer the best range of thermoregulation and warmth for the coldest days of the year. Merino wool base layer bottoms, like the Minus33 Franconia, the Ridge Merino Inversion, and the Meriwool Merino 250 Bottom offer the most warmth due to thicker fabrics that insulate very well on cold days.

If you dig the ventilation panels and optimized breathability, the Icebreaker 260 ZoneKnit and the Icebreaker 200 ZoneKnit are 100% Merino wool designs. In contrast, the SmartWool Intraknit Thermal Merino Bottom features a blend of Merino wool and polyester with enough structure to be worn independently. And while fully synthetic options aren't typically as warm as wool or wool blends, some contenders like the Patagonia Capilene Thermal Weight are closing that gap. Both of these bottoms offer a modern perspective on thermal insulation, increasing the overall warmth of the layer by increasing its ability to offload moisture. We recommend these performance bottoms for high output warmth during cold weather activity, but if you're looking for the warmest model for more sedentary activities or riding the chairlift, stick with the bottoms like the Ridge Merino Inversion and the Minus33 Franconia.

The Patagonia Capilene Midweight Bottoms feature a 100% recycled polyester construction that we consider a synthetic workhorse perfect for year-round use. The Capilene Midweight got the job done whether we needed additional insulation for sleeping out on cool summer nights, a stand-alone legging for spring and fall trail runs, or the perfect base layer for extra warmth during the coldest months of the year.

Breathability and wicking capabilities work together to ensure your skin stays dry, whether pushing the aerobic threshold or hanging out by the fire. To test breathability, we look at fabric thickness and type. We take each option out backcountry skiing, hiking, climbing, and running and test in warm and cold weather conditions. Finally, we evaluate the fabric to see if any moisture is retained within the fibers or if it stays dry as a bone.

Unsurprisingly, the most breathable long underwear bottoms are often the thinnest. Thinner, see-through materials allow air to pass through more readily, thus facilitating optimal evaporation. Some of the most breathable layers in this review are the Patagonia Capilene Thermal Weight. Since the Thermal Weight fabric is rather see-through, we don't recommend wearing them as stand-alone leggings. However, their lightweight design performs incredibly well in a layered system or with spandex bike shorts underneath.

Bottoms like the Icebreaker 260 ZoneKnit, the Icebreaker 200 Zoneknit and the SmartWool Intraknit are perfect for backcountry or Nordic skiing when the temperature is decidedly cold (near to below freezing). And if you're curious, the primary difference between the Icebreaker Zoneknit bottoms and the SmartWool Intraknit is mainly that the ZoneKnit bottoms are constructed from 100% Merino wool while the Intraknit come in a Merino wool blend that feels more rigid. This difference in fabric affects warmth, breathability, comfort, and durability. As a result, we also recommend layering the 200 Zoneknit rather than wearing them as a stand-alone pair of leggings.

The Patagonia Thermal Weight, Icebreaker Zoneknit, and SmartWool Intraknit bottoms receive higher scores because they have special ventilation zones that target specific areas of the lower body that are prone to absorbing body heat and sweat. These body-mapped ventilation panels promote airflow in these areas, offloading moisture while maintaining body heat.

Synthetic fabrics are often known for their rigid structure. An exception to this rule is the Arc'teryx Rho. This layer quickly became a go-to for spring training runs and backcountry skiing due to the ability of the soft, brushed Torrent fabric to wick and shed moisture. Another design that offers less rigidity is the REI Co-op Midweight, but it, unfortunately, didn't breathe as well as its ventilated competitors, often retaining sweat in the waistband and requiring more time to dry fully. While synthetic fabrics are typically more porous than wool, the Midweight features a tightly woven, slim-fitting polyester fabric. On the trail, we prefer synthetics such as the Rho, which features a lighter-weight construction.

Long underwear bottoms like the Minus33 Franconia, the Ridge Merino Inversion, the SmartWool Classic Thermal, and the Meriwool Merino 250 are simply much thicker in construction and not exactly known for their breathability. When we layered these bottoms underneath another pair of pants, we noticed they could not wick moisture away from the body, often accumulating sweat in the fabric, which can get cold quickly. Throughout testing, we observed that the wool contenders typically perform best when sweaty because wool can retain heat, even when wet, much better than thicker synthetic fabrics. Consider these thicker weights for activities such as nightly winter dog walks, hanging out in the yurt next to the fire after a day of backcountry skiing, or keeping you warm on the chairlift on the coldest winter days.

The best you can hope for is a long underwear bottom that'll feel cozy from the ski hill to your bed. Bottoms that fit correctly should also offer the highest level of comfort throughout an entire day of adventures. We put each bottom on to test this metric, wearing them all day and recording our experiences.

Of all the 100% Merino wool options we tested, the Icebreaker 200 ZoneKnit was our clear favorite and quickly became our go-to thanks to the versatility of these bottoms. The high-waisted fit, along with the body mapping technology, helps these tights to fit like a glove. The Merino wool is soft next to your skin, and the fit is modern and flattering. Not far behind was the Icebreaker 260 ZoneKnit, which features the same high-waisted design as the 200 ZoneKnit. The only difference is the thickness of the material, which feels just as soft next to your skin. And though the Minus33 Franconia doesn't have anything near the bells and whistles of the 200 ZoneKnit, they offer a soft and cozy 100% Merino wool design with a thin, elastic waistband that tops our list for all-day comfort.

The SmartWool Classic Thermal are quite comfortable. These bottoms are thick enough to keep you warm and provide enough coverage to be worn independently; however, the fabric eventually sags throughout the day and doesn't have enough shape to hug our curves. Like many other Merino wool contenders, these are best worn underneath another layer or as loungewear around the house. Our testers love the Ridge Merino Inversion, a high-waisted design for added coverage and a functional (yet comfortable) thick elastic waistband. Other lighter Merino wool bottoms like the Icebreaker 200 Oasis and the Ortovox 185 Rock'N'Wool Short Pants are also super comfortable and have a softer feel next to the skin, thanks to their 100% Merino wool fabric.

Synthetic bottoms often feature hollow fibers, resulting in a less comfortable feeling next to the skin. Still, we noticed a couple of options that prove this theory obsolete. The Arc'teryx Rho and the Patagonia Thermal Weight feature a brushed interior or Polartec fleece that's highly comfortable in addition to their superior, high-waisted fits.

Another synthetic option that stands out is the Baleaf Fleece Lined Thermal bottom that offers a fit similar to a modern yoga tight as well as next-to-skin comfort thanks to the fleece-lined interior. The thick, high waistband supplies a flattering fit for a variety of body shapes and sizes, and the spandex in the design allows for enough stretch to support freedom of movement.

One of our favorite blended options is the Ridge Merino Aspect. These bottoms are constructed from 80% Merino wool, 14% nylon, and 6% spandex and feature a thick, high-rise waistband. This stylish waistband highlights the flattering fit of these bottoms, makes them more comfortable next to the skin, and helps keep them in place whether you're out for a training session or doing physical therapy exercises.

We understand that durability is key when purchasing a layer essential for your winter kit. You don't want to invest in bottoms only to find out that they fray, rip, and wear out after only a few uses. To measure overall durability, we observe the wear and tear throughout our testing period until a new product iteration is developed and included in the lineup. We ski, climb, and trail run in each pair of long underwear and record our experiences while layered underneath thicker fabrics or simply worn on their own. We evaluate the quality and craftsmanship of every product by looking at its seams and stitching. After walking through brambles, sliding through canyons, and skinning uphill underneath snow pants, we get a good idea of the durability each layer has to offer. We continue to update this section throughout the year as we gather more information.

If the most durable bottom out there is what you prefer, look for thick fabrics made from synthetic materials. These strong fibers are often stiffer and more rigid, thereby providing better resistance to abrasion and stretch when compared to their Merino wool competitors. The most durable layer we've tested so far is the Patagonia Capilene Midweight. We've tested these bottoms for years and are happy to report they still look great after hundreds of miles and intense use on the trails. The Midweight and Patagonia Capilene Thermal Weight offer a durable elastic waistband and flatlock seams, which inspire confidence in their construction. We only wish the odor treatment was as effective because these layers often smell after minimal use.

Perhaps we were the most curious about how the Patagonia Thermal Weight would hold up during intense activity due to their see-through, ultra-thin design. We are pleased to report that we have experienced no durability issues thus far, though the fabric is some of the thinnest we've tested. We can't imagine it will last as long as a thicker, tightly-woven, and more rigid synthetic design.

Another impressive bottom is the Arc'teryx Rho Bottom, which features a high-quality merrow stitch similar to a welded seam. The only issue we noticed with these bottoms was the tendency for the seams to get a little fuzzy if there was friction between the bottom and our ski bibs; otherwise, they were with us for many training miles without issue. Similar to the Rho Bottom is the Baleaf Fleece Lined Thermal base legging, which we noted also pilled along the thick flatlock seams in high-traffic areas like the inner thigh. We also snagged this bottom on a sagebrush plant during one of our trail runs and ripped a tiny hole in the bottom, though we were pleased when the hole remained small and didn't grow in size even after continued use.

A thicker construction is seemingly more durable than a thin one. However, thicker contenders can snag more easily and pill faster than thinner options. Of the 100% Merino wool bottoms, the Icebreaker 200 Oasis is notable here. The material is tightly knit and seems super burly, even for its thinner construction. The Minus33 Franconia and the Meriwool 250 are a couple of other impressive 100% Merino wool designs to consider if you don't mind a midweight thickness. We were especially impressed by the Minus33 Franconia because the fabric never snagged or pilled after tons of use.

The Kari Traa Rose High Waist features a durable, thick, and well-made 100% Merino wool design reinforced with flatlock seams. Another impressive midweight wool design is the Ridge Merino Inversion, which has held up to rigorous use after multiple seasons of heavy use. Bottoms that integrate Merino wool and synthetic fibers into their construction, such as the SmartWool Intraknit and Ridge Merino Aspect, also tend to wear and tear much better than their 100% Merino wool competitors.

Measuring the overall drying speed for each layer was an important undertaking for us. For each pair of long underwear, we simulated what it would be like to soak and dry each layer for an extended period in the backcountry.

Our results revealed that synthetic fabrics with lightweight construction typically offer the fastest drying speeds. At the same time, Merino wool layers typically require much longer to dry completely.

As always, we love it when a long underwear bottom outperforms our expectations, so we're happy to report that the Patagonia Capilene Midweight Bottom, though considered a midweight fabric, offered the fastest drying speed by a long shot, drying in only 32 minutes.

Other synthetic options that offer fast drying speeds include the Patagonia Thermal Weight and the Arc'teryx Rho, both drying in less than 45 minutes. While 100% Merino wool designs often require longer drying, the 100% Merino wool construction of the Icebreaker 200 ZoneKnit dried almost as fast as its synthetic competition. Completely dry in only 51 minutes, we hypothesize the 200 ZoneKnit increased its drying speed due to the perforated fabric and ventilation panels covering most of these bottoms.

Though most midweight Merino wool bottoms took longer to dry due to a thicker construction devoid of their synthetic competition's porous structure, a few stood apart from the rest. The Minus 33 Franconia and the SmartWool Classic All-Season Merino Bottom are notable here, as are the Icebreaker 200 Oasis Leggings. Of the thickest Merino wool bottoms, we suspect the polyester blend aids in the faster drying speed for the SmartWool Classic All-Season and SmartWool Intraknit.

There is a lot to consider when evaluating the layering ability of each base layer. We tried to assemble various cold weather kits to determine which long underwear bottom performed best within a layered system. Whether layering underneath the grippy inner fabric of our favorite ski bibs or below the smooth interface of our puffy and rain pants, we gave the highest scores to the layers that required the least amount of adjustment, had the smoothest fabric, and promoted mobility rather than limiting our range of motion.

The Merino wool bottoms at the top of our list include the Icebreaker 200 ZoneKnit and the Icebreaker 200 Oasis. We love the ZoneKnit and the Oasis for their smooth wool fabric interface and low-profile elastic waistband, though we noticed some piling on the Oasis from some friction after skinning uphill. The ZoneKnit layered perfectly beneath our climbing pants on a winter mission to climb multi-pitch in Index, Washington.

Other top wool performers include the Ridge Merino Aspect and the 3/4 length design of the Ortovox 185 Rock'N'Wool Short Pants. The five-inch thick waistband on the Aspect bottoms allowed for easy layering, especially if the pants you pull over top fasten at the natural waistline. The Rock'N'Wool Short Pants offer the least bulk in any layered system we assembled due to their 3/4 length, which rests just below the knee, leaving just enough extra room for tucking beneath the very top of our ski socks. We appreciated the Short Pant design when the temperatures heated up during our spring skiing season, leaving more room in our ski boots and less material to absorb moisture when moving quickly uphill.

Our high-performing synthetic options include the REI Lightweight Base Layer Tights and the Patagonia Capilene Midweight. The REI Lightweight features a super low profile and ultralight fabric, which took up the least space in our ski bibs, and a smooth interface between our puffy and rain pants. We love these bottoms for spring skiing and appreciate the extra room for increased airflow and range of motion when pursuing backcountry ski objectives. The higher waist and smooth 100% polyester fabric increase the glide between additional layers over the top, and we love that the waistband, though double-banded, sits above our natural waistline and reduces bulk, allowing other layers to lay flat against the skin.

Another notable option is the SmartWool Classic All-Season Merino Bottom, which didn't impress us with durability. Still, the superlight fabric almost feels like you have nothing on beneath your ski bibs. The Merino wool design also has a touch of nylon, which we suspect allows for a better interface with additional layers. A bit of a surprise in this category was the Ridge Merino Inversion, which features a stripped-down classic design and a higher waist that may take up a little more room than a lightweight option. However, it never reduced our mobility, especially considering it is the only heavyweight option in this review.

We've come a long way since long underwear was made from super thick, itchy wool or a cotton-dimpled suit. With so many long underwear options on the market, it's necessary to take the time to select the pieces that will not only offer a high level of comfort but also meet your performance needs. We hope our in-depth research has assisted you in your quest for the perfect base layer bottoms and that you stay warm and dry throughout the cold months of the year.