(FORTUNE Small Business) – Most of my poker-playing life, I've been a big shark in a little pond, feasting regularly on weaker, meeker fish. But I've always wondered how I'd fare against the game's elite. The World Series of Poker, held every April at Binion's Horseshoe in Las Vegas (see Resources box, page 86), is the preeminent event for all comers--novices and champions alike--to pay their money and take their chances. But the $10,000 entry fee was way too steep for someone like me, just looking to stick a toe or two in the deep end.

The U.S. Poker Championship, however, hosted by the Trump Taj Mahal in Atlantic City, N.J., for the past seven years, seemed a little more accessible: a 19-day tournament with buy-ins ranging from $330 to $7,600, and four different poker variations. I signed up for Seven-Card Stud High-Low and started practicing hard. Seven-card stud is my game, and "high-low" means the pot is divided between the best hand at the table and the worst. If no one has a sufficiently low hand, the high hand takes the entire pot. The buy-in was a relatively affordable $540: $40 to the house, the rest into the prize pool (with payouts to the top 16 finishers).

Joining me at the Taj Mahal that day were 159 other participants, each of whom received a stake of $500 in chips and was randomly assigned to one of 20 tables. The object: to accumulate all the chips in the room. Lose your original stake, and you're done. Betting started at $10 to $20, and to keep the games moving--plus flush out the novices--betting limits were increased every 50 minutes. Ten hours into the tournament, each player would have to ante $300, the low card "on board"--meaning face-up--would bet a mandatory $500, and raises could go as high as $4,000. Not a place for guppies.

Minutes before the 11 A.M. tournament started, I took my assigned Seat 2 at Table 52 and started telling myself, "Don't think about the money. Play your cards, and play your opponent." That's but one of several old but true poker sayings, the most notable being, "If you can't figure out who the worst player at the table is, it's you." I didn't look to be the worst at Table 52, but I was far from the best. How did I know this? Perspicacity. An innate shrewdness in sizing up individuals. And, more important, I recognized the guy in Seat 8 as Thuan "Scotty" Nguyen, winner of the 1999 World Series of Poker and one of the best players on the planet.

Thanks to cable reruns, I'd recently caught tournament highlights pitting an overachieving amateur against Nguyen, a Vietnamese-born pro well seasoned in bluffing and in reading "tells"--the unconscious gestures or inflections that indicate a player's hand or intentions. What I remember most vividly was the amateur, and runner-up, gamely proffering kudos at the end: "You're just too good for me," he said to Nguyen, who'd just won $1 million and barely nodded in icy response.

It's not often that you can test yourself against one of a game's greats. To tee it up with Tiger Woods, you have to be a peer professional, a big-time celebrity, or a wealthy captain of industry. Suit up, grab a glove, and jog out to short at Yankee Stadium, and you'll soon be: (1) tussling with security guards, if not Derek Jeter himself or (2) wearing pinstripes inside a Bronx jail.

That's the egalitarian beauty of poker. No official hierarchies, no handicaps. You need no special equipment to play, only the requisite bucks and a hefty pair of (figurative) cojones. And though anyone can win on any given day, over the long haul, only the player with the most skill--an indefinable blend of wits, wiles, guts, and guile--will leave the table cash-enriched. As such, poker is not gambling; there is no house edge. What could be more entrepreneurial than that? Just you and your disciplined instincts making calculated risks for fun and profit.

Day six of the U.S. Poker Championship was barely 51 minutes old, and already Scotty Nguyen was fixing that laser glare behind his trademark rose-colored glasses on some amateurish sap.

Uh, that would be me.

Glancing at the "cheat sheet" of betting limits, I'd just raised his opening bet more than the allowable $15. A chorus of "too much," "you can't raise that," and "whatta rube"--or "boob," I couldn't tell which--greeted my honest mistake.

Until that error, Scotty seemed bored and distracted, flipping through a magazine and glancing at the dozens of overhead TV screens that lined the walls of the 18,000-square-foot, smokeless poker room. The night before, he'd sat with two other world champions at the last table of the Texas Hold 'Em competition, vying for the $40,515 first prize (and ultimately finishing seventh, which earned him $2,737.50--lunch money for a player of his caliber). Though the buy-in and betting limits were the same in both events, this wasn't Hold 'Em, the game most beloved by high-staked, action-stoked pros. This little seven-stud diversion, his body language told me, was dull and formulaic by comparison.

My plan was to lie low in the early going and not play too aggressively. With the betting limits ramped up every hour, a $500 bankroll could easily be wiped out with a couple of loose hands or even one bad "burn" (a hand that, in all probability, you should win, but due to sheer, dumb luck--often on the last card--you lose). But by raising the world champ, I was no longer lurking in the shadows. I'd proclaimed my presence. Attention, and my bet, must be paid.

Nguyen called. With Seat 1 folding, it was just the two of us, mano a mano, chip to chip.

We both had two cards on board: Scotty showed the four of hearts and a diamond deuce. I had a three and a five, both spades. Nguyen bet the minimum $5, and I immediately upped him to $15.

He smiled tightly and reached for his stack. From the TV reruns, I'd seen that thin grin and slick move before. Like a pitcher tossing to first to see if the batter squares to bunt, he was trying to determine if I would prematurely tip my hand by going for my chips to raise, or by staying at arm's length, possibly to fold. I watched him shake-and-fake, and I didn't flinch. So he called, and the dealer sent more cards around to both of us. His next face-up card: six of clubs. I got an ace of spades to match my three and five--a potential straight flush. It was his turn to bet, and I raised him. He quickly bumped the bet up another $30, strictly an intimidation move. I had better cards on board, so he was just seeing if I showed any weakness.

While I was thinking, You're not dealing with just any chimp, Mr. Bigshot, I said: "Raise $30." All bets were off right there. He couldn't take a chance I'd fill in with the two missing cards and complete my straight flush. Also, there was no percentage in sticking around with just two players' money. He folded his hand. To give him something to think about, I flashed my two down cards. Strictly garbage--an eight and another three. I had bluffed a world champ with a hand consisting of, in poker parlance, bupkis.

It'd make a better story if later we squared off in an even more dramatic showdown for all the marbles. But, alas, it wasn't his day. Or mine. At 12:10, after only 70 minutes of play, Nguyen was one of the first players to tap out. I cruised a while, winning some hands, losing a couple, trying to build the cushion I'd need to withstand the higher betting limits. But I soon got sucked in on a mediocre hand and lost to a heart flush. A rank amateur not only pigged the pot but also swallowed my last tournament chip.

It was around 2 P.M. when I became the 42nd player to fall. Disappointed? Definitely. But not down. Or out. I stayed till the bitter end at 11:15 P.M., more than 12 hours after play began (with periodic ten-minute breaks and an hour for dinner). To succeed in tournament poker it's not enough to be expert in psychology, probability, and money management; top competitors must also have the endurance to concentrate for long periods. In fact, the last few hands illustrated the overriding natural advantage the winner had in outlasting his two opponents: youth.

With roughly equal stakes, 27-year-old Gordon Ernst was literally jumping in his chair after each deal, while sixtysomethings Dusty Ierna and Charles Barker looked bone-weary. Ierna admitted as much: "I'm too tired to even stack my chips."

At 11:07, Barker went all in on an $11,000 raise (that's not a typo) and seemed almost relieved when he lost; he'd probably be asleep before counting all the numbers on his $8,000 third-place check. Minutes later, Ierna graciously took his leave. Too exhausted to stay a moment longer, he said he'd pick up his $16,000 prize money "tomorrow." Ernst, meanwhile, was hugging all well-wishers and posing for every camera with his $32,000 winning hand: an aces-over-eights full house.

As for me, I went to bed cash-poorer but loaded with a pretty good fish tale. After all, I'd gone after one of the biggest sharks in the world and lived to tell about it.