(FORTUNE Small Business) – When Steven Hofmeyr joined a mountaineering club, he expected scenic hikes and leisurely backpacking trips. Instead he found himself clinging, spiderlike, to the side of a cliff, a position made all the more alarming by his acrophobia. "I had a distinct fear of heights," he says.

Hofmeyr, who in September 2000 founded Sana Security, a San Mateo, Calif., company that develops security software, joined that mountaineering club as an 18-year-old in his native South Africa. He didn't realize that it was dedicated to rock climbing. "But they were a fun group of people," he says, "so I started climbing." He scurried up his first route "in a welter of fear" but fought through it and quickly realized he had a natural affinity for the sport. His fear, he says, added to the appeal. "I wanted to figure out how to tame it."

It's safe to say he succeeded—not only in mountain climbing but in ice climbing, the more specialized and technical version of the sport. Hofmeyr, 36, has made three free ascents (carrying ropes but using them only in emergencies) of El Capitan in Yosemite, and solo-climbed 800-foot ice gullies on New England's Mount Washington. This winter he plans to summit California's Mount Whitney. At 14,500 feet, it's the highest peak in the continental U.S.

The three-day trip will require more than 50 pounds of gear, including ice axes, crampons, camping equipment, and telemark skis for descending the mountain after he reaches the summit. Those tools aren't cheap: An ice axe costs $300, and crampons are $200 a pair. Over the years, Hofmeyr says, he has spent about $10,000 on equipment for his hobby. Aside from armloads of gear, the sport also requires endurance—Hofmeyr runs trail marathons to stay fit—and extreme focus. "You live entirely in the moment," he says. "You're not worried about what happened yesterday. You're thinking about where your ax is going to hook in, and is it going to stay there? You think, 'If I mess up here, I could be dead.' It's very intense."

That's not to say he doesn't stop to appreciate the scenery. Part of the sport's appeal, he admits, is the opportunity to see some of the country's most beautiful spots. But occasionally nature turns nasty: Four years ago Hofmeyr and a buddy were ascending a 13,000-foot ridgeline of snow and ice outside Taos, N.M., when they were caught in an avalanche. Hofmeyr was behind his friend, clinging to a bulging rock, when he heard a thunderous crack. "I looked up and saw giant chunks of snow flying toward my head," he says. "I ducked my head down under the rock, and the slab passed over me—I could feel it scraping my backpack. I kept thinking I was going to be buried."

The friends weren't roped together, and Hofmeyr's buddy was swept downhill in a swath of snow 300 yards wide. Incredibly, both men walked away unharmed—though after that experience they decided against pressing ahead with the day's climb. "We'd cheated death," Hofmeyr says. "We decided that instead of continuing we should go back and have a beer."