Coca-Cola Co. will announce "the most significant soft-drink development in the company's history" today amid speculation that it will change the supersecret formula -- and the taste -- of Coca-Cola.

Coca-Cola Co., whose flagship brand has been hurt by inroads made by arch-rival Pepsi-Cola and the company's own Diet Coke, wouldn't say what its momentous announcement will be, but industry speculation yesterday centered on a new formula for the nation's best-selling soft drink that reportedly would make Coke smoother and sweeter-tasting.

The change would not be the first in the soft drink's 99-year history.

There have been at least a dozen changes in Coke's top-secret formula over the years, the most notable being the elimination in 1903 of a trace of cocaine from the syrupy mix.

But while other reformulations of Coke have gone largely unheralded, the company apparently has decided to give this one a big push in an effort to restore some of the brand's faltering share of the soft-drink market.

A recent resurgence of Pepsi and the incredible success of the two-and-a-half-year-old Diet Coke have cut into Coke's market share in recent years.

Details of the expected change in Coke's taste were sketchy and, at times, contradictory yesterday.

"What we're going to get is a reformulation," said Martin Romm, a beverage industry analyst at First Boston. "What the nuances are of the reformulation change, I'm not sure."

Romm said, for instance, that his sources had indicated to him that the new Coke would have a few fewer calories than the current version; other reports said it will have a few more calories.

The consensus seemed to be that the reformulation is based on a change in the beverage's fructose content.

Soft-drink makers have been shifting in recent years from sugar to fructose as a sweetener because corn-based fructose is somewhat cheaper. Coke reportedly will be sweetened with a more potent type of fructose.

Beverage Digest, an industry newsletter, reported last week that a survey by Coke found that respondents preferred the taste of the new formula both to the old version and to Pepsi-Cola.

"Some of brand Coke's problems have been, in fact, because of Diet Coke," said Romm, adding that "one of the major success stories of the industry has been brand Pepsi, much to the chagrin of Coke."

As a result, Romm said, "I think that what Coke is attempting to achieve is to breathe some fire into brand Coke."

Other possibilites for the company's announcement are Coca-Cola's long-awaited Minute Maid-brand orange soda, containing real orange juice, and a reformulation of the grapefruit-flavored diet drink Fresca, which lost popularity when the change in diet sweeteners from cyclamates to saccharin radically altered its taste.

Coke has been bringing out new products at a fast and furious pace in the past couple of years. The development began with the introduction of Diet Coke and continued with caffeine-free Coke and Diet Coke, aspartame-sweetened Diet Coke, Tab and Sprite, as well as the recently introduced Cherry Coke.