"JEFF WILL BE DEAD in three years," says his older brother Greg.

"Huh?" I say.

It's May of 2007, and Greg and I are at a Mexican restaurant in Ogden, Utah, where the Lowes grew up and where Jeff has lived for the past five years. Jeff can't hear us—he's at the other end of a long table with a half-dozen volunteers and guests for his ClimbFest Ogden, an annual climber get-together and fundraiser.

"I said, if he keeps going like this, Jeff will probably be dead in three years," Greg says matter-of-factly.

"How do you figure?"

"If you objectively assess his condition, he was on one cane last year, and this year he needs two. At this rate, he's not far from being in a wheelchair, and after that ..."

That's a grim diagnosis for anyone, let alone a man whom Steve House—winner of the 2006 Piolet d'Or, the highest award in the alpine world—calls "the most important and accomplished alpinist in North American history."

House doesn't hand out many compliments, but Lowe is worthy. The climbing techniques he introduced, refined, and perfected are so common now that they're taken for granted by everyone from beginners to hardened mountaineers. The gear he invented can be found the world over, from Manhattan specialty stores to dusty stalls in Kathmandu. While many alpinists in the seventies and eighties were making their names on high-profile grinds like Everest, Lowe was pushing the embryonic notion that on big mountains—just like on technical rock—the summit alone meant nothing. How you got to the top mattered, and if you didn't do it in a difficult and elegant style, it was, for Lowe anyhow, just another meaningless slog.

"Historically, Jeff is in the top rank," says Michael Kennedy, former publisher of Climbing magazine. "He shifted what people thought was possible. He was going light and fast, applying the lessons learned on smaller technical routes to the big mountains before it became fashionable."

Lowe's vast knowledge and disregard for convention is every bit as relevant today as in the past. "His decades-old vision is still futuristic," says House, who got the beta and photos for his next big project—the mighty west face of Makalu, in Nepal—courtesy of Lowe, who tried it himself once and got buried in an avalanche. "Not all his ideas were practical at the time, but that's the mark of genius."

Lowe's genius, however, hasn't always translated to success in daily life. Often when he applied his unique blend of carefree cha­risma and high risk tolerance to relationships or the business world, he courted chaos: In the past three decades, he's churned through three companies and two marriages, alienating friends and business partners over deals gone bad. "Jeff is very in tune with climbing and the outdoor world," says Greg. "When he stays in that area, he's great. Whenever he strays out of that realm, he's not an equally viable being."

I've come to Ogden to visit Jeff. Our relationship has had its own conflicts over the years, resulting in a few lengthy gaps. I also want to see what he's making of a physical affliction that takes you in only one direction: down. What I find is a predictably unpredictable mix. In many ways Lowe hasn't changed at all—he still wields a strong opinion, mixed with an aw-shucks good-guy demeanor that glosses over past transgressions. "A friend once told me that I was always so manipulative, ‘a silver-tongued devil,' as he put it," says Lowe. "I was never aware of it. But even the most self-aware people are assholes. If we were all entirely self-aware, we'd all be Jesus Christ."

Typically, however, he's also staying active in the climbing community, even though climbing itself is out for him—it might have even contributed to his disease.

Though various environmental and genetic factors can play a role in MS, nobody knows exactly what causes it. Lowe speculates that his case has something to do with the years of suppressed adrenaline inherent to high-pressure climbing situations, as if his body somehow backfired, placing an irreversible strain on his nervous system.

Though MS is treatable, there's no cure, and about 10 percent of its victims suffer from the primary-progressive variety, in which the disease marches on without significant reprieve. Lowe fits this profile; his rate of decline has been rapid over the past six years. He's both resigned to this and wistful about the natural gifts that the disease took away.

"I now realize that I don't need anything that I haven't already got," he says. "That's a great aspect about being physically stopped dead in your tracks. But I would still trade everything I've learned in these past years just for the chance to climb again—even a little."