(FORTUNE Small Business) – Annie Duke is the mother of four children under the age of 9 and a former Ph.D. candidate in psycholinguistics at the University of Pennsylvania, which makes her, she claims, ideally suited to playing professional poker. Duke says her studies gave her a firm grounding in statistical probabilities, while being a parent serves as a reminder of the gambler's first rule: Don't mistake the rent money for your next bet.

Last year Duke grossed $538,000. Here's how it broke down: She played 20 tournaments on the World Poker Tour and World Series of Poker--splashy, televised affairs. She won $340,000, but netted just $70,000 after she reimbursed a silent backer for the $200,000 he put up for her entry fees and then evenly split the balance of her winnings with him. "Tournaments are high risk," notes Duke, 38, explaining why most pros find backers. While a tournament winner can take home as much as $1 million, typically no more than 20 players out of 500 qualify for any prize money.

To offset those odds, Duke makes most of her money in "cash games," simply playing poker at casinos with other players of varying skills. "If you know what you're doing," she says, "you have a 60% chance of winning." Last year Duke grossed $120,000 from cash games, but ever the cautious gambler, she also pursued new revenue streams. As the most visible woman on tour, she netted $30,000 in appearance fees, making, for example, $5,000 for spending a day touting the new HBO Western, Deadwood. (Duke's other Hollywood connection: She has been photographed giving Ben Affleck poker advice.) She's also consulted for ieLogic, a developer of Internet-based, multiplayer poker software, earning some of her compensation in cash ($48,000) and the rest in stock options.

Based in Portland, Ore., Duke says her two biggest expenses are travel and child care, which each cost her about $4,000 a month. Although she's in the business of taking big financial risks, she calmly describes her chips as tools that "allow me to create situations from which I can then try to make a correct decision." That calculus won Duke a $157,140 jackpot in a single tournament in April. Still, the hardened pro hasn't forgotten what happened seven years ago when she first won serious money ($3,500) in a high-stakes game. "Afterward," she says, "I walked into the bathroom and threw up."