Steve McKinney's sport—skiing downhill at 120 or so miles per hour—seems as sensible as jumping off a cliff, which is, in fact, the only other way a human being can achieve such velocity under his own power. Yet inside McKinney's personally designed, Darth Vader-like helmet, he finds existential calm: "The faster my body travels, the slower my mind seems to work. In the crescendo of speed, there is no thought, no sound, no vision, no vibration. It is simply instinct and faith."

Last September in the Andes Mountains of Chile, McKinney's mind must have been at a complete standstill, since he improved his own world skiing speed record to 200.222 kilometers (124 miles) per hour.

McKinney, 25 (at right), is among the 40 or so skiers who compete in the rarefied air of the world's highest and steepest mountains to achieve maximum speed. (Most downhill skiing—in the Olympics, for instance—tests maneuverability as well as speed.)

A speed skier's neck can be broken by wind resistance alone. A fall could burn him literally as well as competitively because his aerodynamically sleek plastic suit can ignite from the friction of the snow. Still, says McKinney, "You might feel fear before the run and sometimes afterward, but not during. There's not enough time."

He got hooked on skiing as a kid in Nevada. Later his divorced mother, a former downhill instructor, remarried and moved to Kentucky. McKinney dropped out of school at 16 and returned West. "Living alone at that age seems strange to some people, but our family always let us kids choose our own paths," says McKinney.

He picked up a high school diploma by correspondence and enrolled at the University of Colorado in 1971 but soon quit to join the United States ski team as a downhill racer. The thrill of that relatively poky sport, in which champion skiers average only 60 mph, soon faded. McKinney also clashed with authorities, whom he labels "harebrained ski politicians." He quit the team in 1973 and tried mountain climbing. On one of his first assaults, a cliff in Yosemite National Park, he fell more than 100 feet and broke his back.

Encased in a crotch-to-neck body cast, McKinney flew to Italy that year to watch the Kilometro Lanciato speed events and do some very careful skiing. "That body cast taught me a great deal about balance," he says.

The next year McKinney returned to Italy—to race this time. He borrowed equipment (speed skiers even have special covers for their boots so the buckles won't cause wind resistance), including skis from the defending champion, who quit when a friend died in a fall. Steve won the event, setting a world record in the process.

Since then the rewards have not been totally spiritual—McKinney's winning purse in Chile was $5,000. (In 1978 he won $30,000 in one race in Italy.) Though low demand for accoutrements like speed skiing helmets limits the endorsement market, McKinney supports himself comfortably by skiing.

His girlfriend, waitress Linda Bagnall, recently joined a commune; Steve lives alone in a 30-foot 1948 Liberty trailer in Tahoe City, Calif. He is doing his own carpentry on a new house near Squaw Valley.

McKinney has no coach ("Nobody else has gone as fast as I do, so what could they teach me?"), but he trains year-round with yoga and month-long cross-country ski trips around Lake Tahoe. He also has resumed rock climbing. "It quiets my mind so I can make the right move quickly," he says. "That's essential in speed skiing. There cannot be any wasted motion. You cannot be wishy-washy."

Speed—the sensation, not the amphetamine—is "the ultimate drug," he says. "What people are seeking with drugs is one clear moment when life can flow through the body without interference from the mind. That's what happens when I ski."