The invitation, explicitly extended to "the craft only," emphasized discretion. Guests of attendees needed to be cleared ahead of time, and a security guard was on hand to reject anyone not on the list. But despite a surplus of glitzy venues nearby, this annual gathering is taking place in rather bland surroundings: the earth-toned clubhouse of a gated community on Las Vegas's suburban West Side. By occupational necessity the crowd is secretive and, if not exactly paranoid, certainly what one would call wary. These are not the sort of people who congregate in Steve Wynn's steak house — or the Venetian's Canyon Ranch spa, for that matter. Sipping Champagne and munching canapés, they constitute a generations-spanning collection of the most skilled advantage players on the face of the earth (to call them mere gamblers would be insulting — and incorrect). All told, they have taken north of $100 million out of the casinos across town. Tonight, though, with the elite players imbibing and talking shop at their own equivalent of the Helsinki summit, Las Vegas's gaming tables will go unmolested.

The 40 or so players at the 12th annual Blackjack Ball are that rara avis among card sharps: math wizards who've spent their professional lives employing subtle and arcane methods to shave bits of uncertainty from seemingly unbeatable games of chance. Nearly everybody in attendance here has managed to flip-flop the casino's odds, essentially turning themselves into the house — and the Bellagios of the world into unwitting marks. They do it by deploying wholly legit strategies that allow them to bet big when they have an advantage, small when they don't. Their techniques include card counting (tracking the dealt cards in a blackjack game to gauge the cards that remain), hole carding (capitalizing on sloppy dealers who unwittingly reveal their cards), and shuffle tracking (following specific clumps of cards through shuffles, thereby knowing when they will be dealt). The most talented advantage players (APs) combine all three moves and augment their arsenal with a hatful of proprietary refinements.

Casinos, of course, despise APs and bar them from betting on games they can beat — if and when, of course, they're found out — on the grounds that they are playing too well. The players, however, claim to be using nothing more than optimal strategies based on information that anyone at the table can utilize. Max Rubin, a former card counter and the Blackjack Ball's host, naturally insists that his guests — who'd make up the star quarry of a show called Casinos' Most Wanted — are perfectly honorable, smart guys rather than wiseguys. "Right here is one of the most trustworthy groups of people that you will ever see: They regularly back one another and play together, doing what are essentially six-figure deals based on handshakes," says Rubin, who now is a partner in a casino in Costa Rica and consults with another in San Diego (by tacit agreement, the players here stay away from Rubin's joints). "You give somebody $100,000 to play with and trust him to tell you how much he won or lost. Most people in the traditional business world would have a hard time with that."

Aside from the camaraderie and the shop talk, there's something else going on here that makes Rubin's fete virtually mandatory for this crowd: the World Championship of Blackjack, a yearly competition of various contests to determine the supreme blackjack master. First prize is just a few thousand dollars in wagered money; bragging rights are what's really at stake. As this year's installment nears its conclusion after a written test and a card-counting competition, guests press in to watch the three remaining players: James Grosjean, a Harvard grad who's known for choreographing complex team plays with small crews of people; Darryl P., a veteran blackjack pro not above enlisting his mother to put down massive bets; and Joe Payne, a burly tournament specialist. Rubin, in the dual role of impresario and referee, occupies the dealer's box of a blackjack table and fans out a deck of cards. Each player has 30 seconds to memorize as many cards as possible, in order, before Rubin gathers them back into a handheld deck.