STEVE EMBER: This year was Charlie Farrow's seventh time in the Arrowhead 135. He teaches social studies in high school. He says every time he does the race, his mind gets tired and starts playing games with him. He starts to imagine himself in the movie "The Wizard of Oz."

CHARLIE FARROW: "I have a recurring hallucination regarding the Wizard of Oz. I always have this vision of the trees coming after me, and then I also have this vision of the Emerald City, but I can't ever get to it."

Being alone in the wilderness is also part of the difficulty of the race. The trail begins at International Falls, on the Canadian border. It passes through a national forest and around and over frozen lakes. Minnesota is known as the land of ten thousand lakes -- in fact, it has closer to twelve thousand of them.

Three aid stations and nine shelters are spaced along the trail. But during the race, the competitors spread out far apart, and Mr. Buffington says the biggest danger is being far from help.

JASON BUFFINGTON: "Both years that I've biked it, even though it's taken less than twenty hours, there are times where for six-and-a-half hours, in the middle of the night, twenty below [zero], you don't see a soul, and if anything happens, you're out there on your own."

BARBARA KLEIN: Jeremy Kershaw is a forty-year-old heart nurse. He has completed the race for the past three years. First he skied, then he biked, and last year he went on foot. He had about thirty-two kilometers to go when he found a racer struggling on the side of the trail.