"One hundred seven." I tremble in disbelief as I lay down WAYBILLS and announce its ungodly score to take a 99-point lead in the most important ­Scrabble game of my life. My opponent, former national and world champion Brian Cappelletto, replies with RADICATE for 65, but he's dead. I win 459-410 to take sixth place in the 2005 National Scrabble Championship. This outcome seems almost ludicrous: I was in 72nd place out of 87 halfway through the 28-game marathon. But in the last 14 games, I lost only once against the strongest field I'd ever faced. I emerged as one of the top 10 Scrabble players in North America.

The National Scrabble Association sanctions several tournaments every weekend across the country. But with a $25,000 prize at stake, the National Scrabble Championship (in 2006 renamed the U.S. Scrabble Open) is the highlight of the circuit; serious players consider it the most prestigious tournament in the world. (The World Scrabble Championship uses a different, larger dictionary and isn't officially rated.) ESPN tapes the best-of-five showdown between the top two finishers and airs an hour-long show about the competition each fall. It's must-see television. Last year, former world champion ­Panupol ­Sujjayakorn of Thailand made the finals. That he can't comfortably speak English is irrelevant; he's a wicked machine at executing solid Scrabble strategy.

When playing top-notch opponents like Cappelletto or Sujjayakorn, I assume that they, like me, have memorized all 83,667 valid words of up to eight letters. Even then, the game requires the foresight of chess and the inferential strategy of poker. I must both maximize my score on the current turn and keep strong letters on my rack to increase the probability that I can maximize my score on future turns. I further aim to squelch opponents' opportunities by guessing, based on their previous plays, which tiles they are most likely to be holding. By tracking tiles as they are played, I can also deduce exactly which tiles my opponent has in the endgame and plan my final plays accordingly.

In other words, competitive Scrabble is a math game, and the level of strategy involved is one reason I keep playing. To sharpen my skills, I collaborated with John O'Laughlin, a fellow Scrabble expert, to write an artificial-intelligence and analysis tool called Quackle. (Anyone can try it--we made it free and open source--at quackle.org.) I usually play five games a day against Quackle and win about half the time, but I find the program most useful for analyzing my tournament losses: it can show me what I missed.