After surgeons removed his cancerous thyroid gland in 1999, chemical engineer Scott Hagwood found that without the hormone it produced—which aids in mental clarity—he couldn't get through a newspaper or a long conversation. "It's amazing," says Hagwood, 39, of Fayetteville, N.C., "how difficult it was to concentrate."

Frustrated but determined, he passed the time during post-op radiation treatments studying a memory-training book, using its techniques, such as associating a word or number with a visual image, to recall sequences of playing cards. Soon, he discovered, "I could remember five or six cards in a row. I thought, 'Wow, this really works.'"

And how. Hagwood, now in remission, made his mind so nimble that in March he captured his second-straight National Memory Championship—winning the Mr. Memory title by, among other feats, recalling the order of cards in an entire deck in under four minutes and a list of 97 random words in 30. Tournament founder Tony Dottino says of Hagwood's 2001 debut: "Everyone looked at each other, saying, 'Where did this guy come from?'"

Raised outside Knoxville, Tenn., Hagwood was an average student with an unremarkable memory who struggled through college. Beyond the contests—he tries for the world title in London in August—Hagwood's powers have helped him prepare stepdaughter Kristen, 16, for her SATs. Wife Janet, 45, relies on him to match names and faces at their 2,000-member church. Still, he sometimes forgets to pick up the milk en route from work. "When I do that," says Hagwood, "Janet calls me Mr. Selective Memory."