Once a month, these five San Francisco sommeliers get together and stay up late—very, very late—tasting wines and making a delicious meal.

Some professionals--like IRS auditors or forensic pathologists--go to great lengths to separate their careers from their personal lives. Sommeliers, on the other hand, take every opportunity to combine the two. In San Francisco, five of the city's best regularly mix business and pleasure: They gather after hours at one of their restaurants, invade the kitchen and sample wines from around the world--from grands crus to table wines--until four or five in the morning. Wines are tasted blind, so no one knows what he's drinking until someone guesses it right.

The godfather of the group is Larry Stone, 49, the sommelier at Rubicon and one of the country's premier wine authorities. Stone began tasting wines blind when he was seven, inspired by sophisticates like James Bond and The Avengers' John Steed. At Rubicon, local sommeliers would sit in on his weekly staff tastings, then come back after the restaurant closed for the night, especially after Rajat Parr began working for Stone in 1996. Parr, 28, was born in India and was exposed to wine by a British uncle and a Culinary Institute of America education: "I didn't have a girlfriend or a house, so I could spend every penny on wine, and I did." Now the sommelier at Fifth Floor, Parr has brought jaw-dropping bottles to the tastings, including 1971 Romanée St. Vivant and 1928 Latour Blanche Sauternes.

At the tastings, Stone and Parr are joined by Emmanuel Kemiji, 40, a consultant for the Ritz-Carlton who is also the owner of, and winemaker for, both Miura and Candela; Peter Birmingham, 42, the sommelier at Elisabeth Daniel; and William Sherer, 37, the wine director for Aqua, Pisces, and Charles Nob Hill. While the sommeliers love one-upping each other, they come together mainly to share discoveries. "In other cities, sommeliers compete. In San Francisco, we exchange wines like they're cups of sugar," Kemiji says. Each selection is decanted or kept in a paper bag so there's no peeking at labels. "A label can profoundly influence you," Birmingham says. "You have to hide the corks, too; it's a tough crowd," Kemiji concurs. Identifying the wines correctly comes with practice and experience. "It's taste memory combined with deduction. Exceptional tasters, like Larry, identify the flavors and nail the wine; others are more analytical and figure it out by the process of elimination," Sherer says.

Many tastings are organized around a theme; recently the focus was Rhône-style wines for around $30 or less. Stone opted for the supple, vigorously fruity 1999 J. L. Chave Selections Mon Coeur Côtes-du-Rhône from France; Parr, who knows Stone's tastes well, identified the wine in seconds. But Kemiji's choice, the plummy 1998 Carver Sutro Petite Sirah from California, produced in tiny quantities (130 cases), stumped the group. No one could guess the country of origin or even the grape variety, though each sommelier liked it enough to consider it for his wine list.

All that tasting inevitably makes the sommeliers hungry. Invariably, one of them will put down his glass, roll up his sleeves and head for the kitchen to prepare a meal. Birmingham might fix his legendary scrambled eggs with truffle oil; Sherer uses cheese-plate leftovers to make croque-monsieurs. Whether the meal counts as a late dinner or an early breakfast, it fortifies the sommeliers for their biggest challenge: finding a cab home at 5 a.m.