Faces shining, palates yearning, they have come from as far away as Kansas City to taste wine in the presence of Robert M. Parker Jr. They are yuppie elders, affluent and learned, yet they sit in near-rapture as they inhale the heady wisdom of the One Voice of the wine world. "With him it's reverential," says Rodger Helwig of Manhattan's International Wine Center. "Almost hero worship."

Parker, 40, is at the Center conducting a one-day seminar on the wines of the Rhône, which used to be cheap until he started praising them in his wine guide 10 years ago. He speaks to the class unaffectedly, joking about the wife of a famous wine maker "whose voice has a decibel level that gives you headaches." Class members respond with the most arcane questions they can muster, about the percentage of Mourvèdre grape in Châteauneuf-du-Pape or about the scent of bacon fat in Côte Rôtie. They seek answers less than acknowledgment, an opportunity to share a (preferably pretentious) word or two with the author of The Wine Advocate, a one-man publication that comes out six times a year, goes to about 23,000 subscribers and has an effect on the wine trade far beyond its modest circulation. "There has never been anybody in the wine business with more impact on what to buy," says Mike Goldstein, owner of Park Avenue Liquor in Manhattan.

While wine drinking is an ancient and respected pastime, wine writing is newer and more suspect. Goldstein puts it bluntly: "Parker cannot be bought, as I think other wine writers can." Parker has achieved preeminence while eschewing most of the perks of the trade, including sumptuous lunches with château owners. Mostly he drinks alone, and he spends about $60,000 a year buying what he tastes. Working out of a cramped room in his rural Maryland home, he samples about 200 wines a week and bluntly informs readers of his opinions (e.g., "Smells of cat's urine, sour, thin"). He inhales, tastes, spits out and rates a wine in minutes. "When I see a person pondering, it tells me he doesn't know what he's doing," Parker says.

The man who might be the most influential American pamphleteer since Thomas Paine wasn't even interested in wine until he went off to France in 1967 to visit his college sweetheart, Patricia Etzel, who was studying there. During his stay, Parker started drinking vin ordinaire because Coca-Cola was too expensive. They were married in 1969, and the bride soon learned what it was like to live with a wine enthusiast: cold. He stored wine in their suburban Washington, D.C., studio apartment, kept the temperature in the low 60s and suggested she wear a sweater if she were uncomfortable.

After graduating from the University of Maryland law school in 1973, Parker went to work for the Farm Credit Banks of Baltimore. He started his wine guide in 1978 and for the next six years worked at both jobs, sometimes putting in 90 hours a week. In 1984, when he was fully vested in the company pension plan, he retired. Since then, he has put out three books (Bordeaux, Parker's Wine Buyer's Guide and The Wines of the Rhône Valley and Provence), and the Parkers have adopted a South Korean girl, Maia, 1. He is doing so well financially that they are expanding their modest ranch house.

Parker's success is probably due less to his reputation for incorruptibility—he once passed up a château owner's proffered gift of a Napoleonic-era music box—than to the simplified 100-point rating system he devised for The Wine Advocate. It's as easily understood as a junior-high-school report card, but the grade curve is strictly graduate school. After 10 years of tasting, the stringent Parker has awarded perfect scores of 100 to only 15 wines, none from such esteemed châteaus as Haut-Brion or Lafite-Rothschild. Critics of his easy-to-follow system argue that subscribers, who pay $30 a year, buy wines not because they like them but because his ratings tell them they should.

So influential are Parker's opinions that after one famous château changed wine makers, there were rumors in France that the man was dismissed because Parker had consistently downgraded his wines. "I don't think I have that much impact," he says. "My ego isn't that big." Parker also denies that his ratings cause wine prices to rise, but that's a hopeless protest. Only the declining American dollar has a more inflationary effect on prices than a favorable Parker rating. A wine from the Rhône vineyard La Mouline cost about $12 a bottle 10 years ago; today, after receiving three scores of 100, a La Mouline costs about $200. That's the kind of economic success story that gladdens the hearts of French wine makers, who inundate Parker with hundreds of samples on his frequent trips to Europe. "It's a nightmare," he says. "I can't get all the bottles into my hotel room." Perhaps the supreme compliment to the power of The Wine Advocates that these Frenchmen listen respectfully when Parker speaks their language with his heavy American accent. "Nobody laughs," he says. "And if they do, they make sure I've left the country."