(FORTUNE Magazine) – The Lucky Chances casino in Colma, Calif., a town just south of San Francisco known mostly for its endless cemeteries, has none of the glitz of a Vegas gambling palace. With its scruffy carpeting and whiteboards announcing tournaments, it looks more like a bingo parlor. That's just as well for J.P. Massar, who does not come in here to drink in the atmosphere.

Massar, a short man in a polo shirt who affects the studied anonymity favored by a certain kind of serious card player, is hunched over a shrinking pile of matte poker chips. He tunes out the din from the men slamming dice cups nearby in a local game called Pai Gow Poker. And while the other nine men at his poker table banter and joke, Massar avoids any discussion or even eye contact. He's throwing in hand after hand. Massar will not bet on any but the strongest hands. Loose betting is for suckers.

A few tables over sits Massar's friend and study partner, Stephen Landrum. With a scraggle of beard and a huge Stetson, Landrum is comparatively flamboyant. But like his friend, Landrum didn't come for the company. Most of the time he looks like a scowling Bob Dylan surrounded by a group of genial truck drivers. He, too, pushes hand after hand into the center of the table.

Scenes like this are played out nightly in casinos around the country. The only difference: This casino is in the heart of Silicon Valley, and Massar and Landrum are dropouts from a culture famous for risk-taking at work, not at play.

Massar, 44, is an MIT Ph.D. who programmed supercomputers at the pioneering but failed Thinking Machines Corp. Landrum, 38, designed and programmed computer games for two decades before being laid off two years ago from the once highflying games company 3DO. "Programming can be really intense," says Landrum. "I got burned out." Now both are professional poker players, members of a small fraternity of techies who've turned their considerable analytical talents to winning in the Valley's "card rooms," as they're technically known.

Success in poker, the only game for serious players here, depends on a feel for the complicated mathematics of the cards and the bets, as well as a sense of the psychology of the game. So you might expect the Valley's card rooms to be filled with techies who've scored big in the Internet boom.

That's not the case. Programmers and engineers are not gamblers by nature. However much money they might have to lose, they're not eager to give it away in a high-stakes card game in which they'll be outclassed. And few have the patience to learn to play well. In a world of multimillion-dollar option payouts, who needs to sit at a card table waiting for the rare good hand?

And yet a few do it, and not only those who've left the life behind. There are also successful engineers and a few technology executives who sneak out of their offices in the dead of night. In a milieu famous for nonconformity, some are fleeing Silicon Valley's most constricting type of conformity: the 24-hour work cycle. "There's a culture of card players, and a culture of good, clean-living wage slaves," philosophizes Barry Tanenbaum, a training manager at computer giant Compaq and a regular in the card rooms.

The irony here is that although, as Tanenbaum happily puts it, "card players are not your finer citizens," of all the vocations you can choose in Silicon Valley today, it's poker that most rewards patience and skill over hype and cash.

Two days after the night at the Lucky Chances, Landrum e-mailed to say that he had won a poker tournament and netted $1,580. It was the first time in a while that anybody in Silicon Valley had bragged to me about a four-figure payout, and it seemed hard won and well deserved.