DEAN KARNAZES IS THE KIND OF GUY who does pee while running, as detailed in Ultramarathon Man, along with other amusing anecdotes of the running life, such as puking all over his company Lexus after his first ultra, in 1993, and passing out spectacularly at mile 72 of his first Badwater attempt, in 1995.

This past June in Squaw Valley, California, Karnazes arrived at the 100-mile Western States Endurance Run in top form, sauntering toward the medical check-in flanked by his wife, Julie, a dentist; kids Alexandria and Nicholas, ages ten and seven; and a representative from The North Face, which sponsors the event and has sponsored Karnazes off and on since 1999. Western States is the country's oldest and most prestigious ultra trail race, and Karnazes was eager to earn a special 1,000-mile silver belt buckle for completing the event for the tenth time. He wore snazzy red North Face surf shorts and a pair of North Face trail shoes he helped design, and his veins popped commandingly from his calves, which were shaped like paleolithic clubs. People snapped his picture while he ate lunch or strolled around, and, at one point, a man in running clothes sidled up and excitedly thrust out his hand.

"Hi, my name is Mark, and I just read your book," he said. "I want you to know it really inspired me. This is my first 100-mile race."

"Hey, thanks, man. Glad you enjoyed it. Good luck tomorrow," said Karnazes, flashing his high-voltage smile.

"How much more do I have to prove here?" asks Reed. "I'm not getting any younger." But then she laughs. "I really would like to run 500 miles," she says. "How sick is that?"

"Karno" appears at ease with his celebrity, a status that was, until he came along, completely foreign to the world of ultrarunning. For most competitors, Zenlike suffering is its own reward, but Karnazes is either a more social or more pragmatic animal. After weighing in at race headquarters (157 pounds at five foot nine, blood pressure 108/70, heart rate 40 beats per minute), he jogged to the concession room to sign his book.

To almost everyone's surprise, including his own, he says, crowds have flocked to Karnazes's book signings, lining up to hear his moving account of how he runs to live life to the fullest and to honor the memory of his sister, who died in a car accident as a teenager. "I like to get up there and tell my story," he says. "If it's inspirational, if that's what people get out of it, it's kind of a rush, actually. Almost like an ultra in a sense, like a drug, and then when you're finished, people are applauding."

Karnazes's unlikely media breakout is all the more surprising given that he's not even the world's best ultrarunner, though both he and Reed routinely finish near the top of the pack. But the two have managed to shake up the sport in ways that other ultrarunners can't—or won't. They've done this in two ways: first, through their over-the-top pursuit of brutal distances, and second, through their wholly unapologetic pursuit of fame. Since Karnazes started competing in ultras in 1993, he's won only one major title, the 2004 Badwater, where he bested Reed. But no one can touch Karno in the marketplace.

A cross-country, volleyball, and surfing star in high school in San Clemente, California, and a windsurfer at Cal Poly in San Luis Obispo, Karnazes started running long distances on his 30th birthday, when he jogged all night to stave off an early midlife crisis. By the late 1990s he was wowing the Bay Area by soloing the 199-mile Relay from Calistoga to Santa Cruz, a feat he's now accomplished seven times. He ran the first South Pole Marathon, in 2002, posing nude post-race at the bottom of the world. Last year, he ran 262 miles, ten marathon distances in a row, to raise money for Organs 'R' Us. Did we mention that he cross-trains by surfing, rock-climbing, and mountain-biking?

"He's a dream," says Katie Ramage, who manages The North Face's athlete team. "He's smart. He's driven. He's photogenic. We have a category called media darling, and he gets the highest ranking." The cosmetics company Kiehl's, which sponsors Badwater, underwrote Karnazes's book tour, a fine complement to its line of Vital Sun Protection and Facial Fuel Energizing Moisture Treatment. Dashing into the Kiehl's store in Las Vegas for a signing last summer, Dean joked to the crowd that he was late because he'd had to mousse his chestnut locks.

It's a tough act to follow.

"Have you seen him? He's great-looking," groans Pam Reed. She was also at Western States this June, sans entourage. Her husband, Jim, would serve as pacer, chauffeur, and hander-over of Red Bull and Ensure. Reed almost didn't come to the 2005 event, but, like Karnazes, she wants to nail ten of these babies, and this was number six. Lately, though, she'd been pushing herself too hard, first on her Arizona highway solo, then by running a London Marathon, followed the next morning by a double Boston ("That was a mistake!" she said afterwards), then running 178 miles at a 48-hour race in France.

On race day, bounding into the aid station at the top of a 36-switchback climb at mile 47, Karno looked as fresh as trailside lupine. He unfurled his shirt, poured ice water over his head, and filled his bottles. "I feel good," he said. "I enjoy watching the sky." Then he grabbed a cookie and chased off after the Tanzanian in 11th place.

Reed, for her part, was struggling. At 5:30 a.m., she was slogging the remaining few miles en route to a 25-hour-59-minute time, four hours before the race's 30-hour cutoff. Her husband had quit pacing her after 20 miles, leaving her to navigate the nighttime forest on her own. "This is the worst ultra I've ever run," she said at mile 96.8. "Everything hurts. Everything." Karnazes, meanwhile, had leaped across the finish line in seventh place at around 11 p.m. the night before, finishing in 18 hours and 14 minutes. After a quick water douse, he peeled off his socks. Not a blister or blackened toenail in sight. "Hey," he said, standing up and shaking his arms. "That was fun!"

No wonder Reed wants to gag on her GU2O.