Sheep Mountain, Alaska
THE RACE: "CAUTION: Weather can be extremely cold!" reads the race Web site. That's your first hint that this is a serious undertaking. Up until the starting gun, you can choose between a bike, skis, or snowshoes to take you 100 miles alongside the 10,000-foot Talkeetna Mountains. Even surrounded by fellow competitors, most first-timers from the Lower 48 will find it the most pristine wilderness environment they've ever experienced. HIGHLIGHT: Finishing. No other winter race in America offers a more formidable challenge. CRUCIAL GEAR CHOICE: Bikers have the advantage. Arm your frame with aggressive, studded treadstry Nokian's Extreme 296 ($112; www.nokian.com). And run your tires soft.THE LOWDOWN: Entry fee $250; 907-345-4505; www.iditasport.com.
The Mount Taylor Winter Quadrathlon
Grants, New Mexico
THE RACE: The "Quad" entails a 13-mile road ride, five-mile run, two-mile ski, and one-mile snowshoe from the town of Grants to the top of Mount Taylor, an 11,301-foot extinct volcano in west-central New Mexico. After a 4,800-foot ascent, and a brief medical check on top, you reverse the entire course and head downhill back to town. HIGHLIGHT: Hopping on your bike for the final leg of the race, a fast 13-mile descent to the finish line. CRUCIAL GEAR CHOICE: Climbing skins are essential for the last mile of the cross-country ski climb, dubbed Heartbreak Hill. THE LOWDOWN: Entry fee: $75 ($55 before Feb. 1); 800-748-2142; www.mttaylorquad.org.
The Elk Mountain Grand Traverse
Crested Butte, Colorado
THE RACE: Starting at midnight from Crested Butte, 100 teams of two ski 39 miles over two 12,000-foot passes and through some of the most rugged mountain terrain in the state en route to the summit of Aspen Mountain. From there, it's a glorious 3,000-foot drop on groomed runs to the finish line. HIGHLIGHT: Besides the guarantee you'll never race in a more beautiful winter setting, the finish line fiesta at Aspen's base area is well worth the 40-mile grind. CRUCIAL GEAR CHOICE: Most participants prefer lightweight cross-country skis with climbing scales and a metal edge (see left). THE LOWDOWN: $100; 970-349-1019; www.elkmountaintraverse.org.
Son of Inferno Pentathlon
Glen, New Hampshire
THE RACE: Run seven winding miles, kayak six miles of Class I and II rapids, and pedal the 18-mile climb to Pinkham Notch at the base of Mount Washington. Okay, now stomp up 4,000 feet to the top of the most storied backcountry ski slope in America: Tuckerman Ravine. Finally, slap on your skis for the 2,000-foot drop to the finish line. HIGHLIGHT: Nine soloists completed last year's inaugural event. Start training now and you could own a course record. CRUCIAL GEAR CHOICE: A helmet, for skiing Tuck's 50-degree headwall. THE LOWDOWN: $100 individual, $500 team; 603-356-0131; www.friendsoftuckerman.org.