LONDON—It was a tense moment in Christie’s London boardroom. During a preview to entice buyers, the house’s representatives were about to open a bottle of rare old Champagne with perfect provenance: Moet & Chandon’s Cuvee Dom Perignon 1921, direct from the late Doris Duke’s cellar, where it had rested since its purchase in 1936. The bottle, one of several in the famed heiress’s collection that were slated for auction at Christie’s New York in June 2004, was from the very first vintage of the world’s most iconic luxury wine. Could an octogenarian Champagne still show its stuff? Would it even have bubbles?

“There was absolute silence in the room,” says Richard Brierley, Christie’s head of North American wine sales, who had hand carried the Champagne from New York. “I held the bottle to my ear as I wiggled out the cork, and there was just the slightest hiss of carbon dioxide escaping. We knew then that this 83-year-old wine still had life.”

Brierley poured the first sip for Dom Pérignon’s current cellar master, Richard Geoffroy, who had traveled from the French region of Champpagne for the event. He had never before tasted the 1921. His verdict: “Fabulous.”

At the 2004 auction, three bottles of that rarest of rare vintages—the ones in the Duke trove were the only known examples—sold for an astonishing $24,675 (including buyer’s premium), or $8,225 each. Prices for collectible Champagnes have been on a tear ever since. Last April, a single bottle of Krug Collection 1949 fetched $4,541 at Acker Merrall & Condit in New York. The next month, back at Christie’s New York, a case of Dom Perignon Rose 1978 reached $28,440, a leap of 749 percent over its previous sale price, according to Wine Spectator.

In another sign of its current market strength, 102 lots of Champagne, rather than the usual trophy Bordeaux or Burgundy bottles, led off the high-profile $7 million auction of wines from the cellar of the late collector Steven Verlin held in May at Hart Davis Hart, in Chicago. “We decided that Champagne is so exciting it would start off the sale with a bang,” says Hart Davis Hart’s consignment director, Ben Nelson. “Not too many years back, bubbly was usually pushed to the back of the catalogue.” As Charles Curtis, wine educator for Moet Hennessy USA, sums it up: “Collectible Champagne is simply the hottest category in wine.”

The sparkling upswing is being driven by “relatively young” buyers, according to Brierley: “They see this as a category that has not been overpopulated.” That’s an Englishman’s diplomatic way of saying that the market for elite Bordeaux and Burgundies swarms with aggressive buyers who have pushed prices to stratospheric levels. Just one example from this year: An imperial (equal to six regular bottles) of Chateau Latour 1961 brought $65,725 at Acker Merrall on June 27.

By comparison the cost of even the most sought-after sparkling wine seems modest, despite the recent run-up. In last May’s Verlin sale, for example, a jeroboam (equal to four regular bottles) of Moet & Chandon Brut Imperial 1961 sold for $3,824. Time, in Brierley’s view, can endow such bottles with “immense subtlety and gentleness.”

A taste for well-aged Champagne, it must be said, goes against the common wisdom that bubblies are best consumed while still “fresh”—ideally upon purchase. Indeed, some collectors believe that the first duty of an ageworthy wine is to be red. The same folks are known to lay down only select whites, such as the Burgundy Montrachet and the dessert wine Chateau d’Yquem. But the best sparkling vintages can, like their still counterparts, gain nuance through decades of slow maturation.

While tannins bolster reds for the long haul, the key to Champagnes’ graceful aging is “buckets full of acidity,” according to Stephen Charters, professor of Champagne management at Reims Management School. In addition, two of the three grapes used to make Champagne, Pinot Noir and Chardonnay, just happen to be the bases of red and white Burgundies, wines that are frequently aged with great success. Average nonvintage bubbly—what most people drink at weddings, graduations and birthday parties—is more about fizz than refinement.