The "beautiful drink--for beautiful people" is being challenged, not by a competitor, but by its own parent firm, Coca-Cola Bottling Co.

By the end of the week, Diet Coke (with but one calorie per 16 ounces) will be on the shelves of major supermarkets in the Boston-Cambridge area and throughout New England.

Yesterday, shipments of Diet Coke in liter and two-liter sizes were sent to some local markets, including the Store 24 chain.

But Harvard students have already been tasting cans of Diet Coke, which company executives hope will appeal to diet drink customers who don't like Tab because of its cosmetic--some say feminine--image.

"We hit the streets with [Diet Coke] today and the orders are staggering," a Coca-Cola executive said yesterday. Tab is currently the world's most popular diet soft drink.

Cans of Diet Coke have been available on campus for about the last three weeks as company officials followed a policy of gradual introduction to the diet drink market.

"A lot of people get burnt out on Tab but still need the caffeine, so they buy Diet Coke," said Anne M. Coyle '84, who works at a candy store in the Freshman Union.

The Coca-Cola Company added Diet Coke to its soft drink roster to "expand in an expanding market," John E. Bazaire, central division manager of New England Coke, said yesterday.

Bazaire predicted that by 1990, the market share of diet drinks may double to 30 percent.

Coke first test-marketed its new product in New York during August, according to Bill Elmore, the company's New York regional manager. Elmore said New York was selected because "there's a high low-calorie market [here]--around 30 percent of the total."

In September, Diet Coke reached other markets, including San Diego, Denver, and Rochester, N.Y.

"Sales have so far been much better than we expected." Bazaire said, adding that advertisements for the product in New England will begin next week.

"We're confident it's going to be a winner," he said.