(FORTUNE Magazine) – It's Dec. 31, 1999. You're hosting the party of the millennium. When the clock strikes midnight, you raise a glass to toast the year 2000. Sadly, that glass is filled not with Dom Perignon but with Sprite, one of the few drinks with bubbles that you've been able to find since Columbus Day.

Yes, it's yet another Y2K problem: There may not be enough champagne to go around for next year's millennium parties. For starters, suppose half of all American adults who wouldn't usually drink champagne get swept up in the excitement and have one glass each next December. And suppose that people who like champagne each buy one extra bottle. Demand for champagne would shoot up by 36%, according to Gloria Ferrer, a sparkling-wine maker in Sonoma, Calif. But the most exclusive French champagne houses will produce, at most, 10% more wine than they did this year, and only a fraction of it will make its way to the U.S. "There's a finite supply of the grandes dames in a regular year," explains Michael Kapon, CEO of New York City wine store Acker Merrill Condit. "So producers are feeling tremendous demand for next year. Some stores will get three bottles of Cristal, if that."

The projected shortage is due in part to the simple fact that making champagne takes time. The grapes you'll drink next year were harvested in 1997 at the very latest, and some prestige wines take much longer: Veuve Clicquot, for one, will be delivering bottles from the late 1980s for the year 2000. "No one was thinking about the millennium that far ahead," says Bernard Paillon, vice president for marketing at Schieffelin & Somerset, which imports Dom Perignon and Moet & Chandon. Even if someone had been, it would have been difficult for them to do much about it: French regulations limit the amount of real champagne that can be made each year.

The knowledge that there is a finite supply is already having its effects. Schieffelin & Somerset has its entire 1999 supply accounted for; by comparison, it hadn't allocated its 1998 supply until May of this year. The firm's distributors, in turn, are already talking to their key customers to figure out how many bottles each wine store or restaurant might get.

Some people expect the French stuff to be gone by September--and the best sparkling wines from California or Spain may not be far behind. So it's no surprise that some people have already started paying in advance for next year's bottles, creating an informal champagne futures market. It may sound extreme, but it's worth considering if you absolutely must have Cristal next New Year's Eve, or if you just want to be sure you won't be toasting 2000 with club soda.

--Eileen P. Gunn