As Giant Food and Safeway continue to slug it out for the bulk of Washington's grocery business, one small independent -- Jumbo Food Stores -- is quietly but steadily gaining clout as an important player in the supermarket industry, according to a new study of Washington-area food sales.

The family-owned, Landover-based Jumbo Food Stores increased its Washington-area sales by 30 percent last year, ringing up $159 million, or 4.5 percent of all food sales made in the area, according to the just-completed annual market study of area grocers done by Food World, a grocery trade journal based in Columbia, Md.

The $159 million in sales makes Jumbo the third-largest grocery chain in the Washington area, up one notch from last year's ranking, when Food-A-Rama ranked No. 3 with sales of $156.6 million. This year, with sales dropping slightly, Food-A-Rama is the fourth-largest grocer, with sales at $155.5 million.

Jumbo is still a long way from catching up to the two major chains, Giant and Safeway, which together take in about 75 cents of every dollar spent on groceries in the area.

Giant alone accounted for 42 percent of the market for the year that ended April 30, with annual sales of $1.5 billion. That represented a marginal increase in market share over last year, when Giant had 41.5 percent of all local grocery sales.

Safeway, with annual sales of $1.2 billion, has a 32.6 percent share of the market -- a full percentage point above last year's level.

"Giant is a juggernaut; it just keeps going at full gears," said Jeffrey Metzger, who with his partner Richard Bestany, owns two weekly publications: Food World, which covers the Washington-Baltimore market, and Food Trade News in Pennsylvania.

Food World's annual study of the local supermarket business is considered one of the most accurate assessments of the industry in this highly competitive market. Its data is based on information furnished by retailers and distributors who supply goods to local stores.

Despite Giant's continued leadership in the very competitive local market, the "real story is Jumbo's success," Metzger said.

A few years ago, Jumbo ran very traditional supermarkets. But Jumbo has taken an active role in this "warehouse" grocery store market, opening eight Shopper's Food warehouses. "Shopper's has done the best job with the warehouse concept -- and consistently," Metzger said.

Despite its rapid growth and rise to the third place in the market, Jumbo does not have grand ambitions to beat the leading two firms, said Michael Herman, Jumbo's senior vice president. "We're really small potatoes," Herman said. "We're in the minor leagues compared to our competition. We know our place. We're not trying to beat the other guys."

Herman said Jumbo planned to open two more Shopper's Food warehouses this year in suburban Virginia.

Behind Jumbo and Food-A-Rama was the Great Atlantic & Pacific Tea Co., which retained its fifth-place rank. Close behind were Magruder's, Cook's Supermarkets, Food Town/Price Chopper, Fresh Value and Pershing's.

All but one of the independents (Cook's) opened at least one new store last year. Giant, on the other hand, stayed with the same number of stores -- 93. Safeway opened one more, bringing its area total to 125 stores.

The busiest store in the area was Giant's new store on Rockville Pike, which rang up $35 million in sales, knocking the "social Safeway" on Wisconsin Avenue out of first place. With $33 million in sales, the "social Safeway" ranked No. 2 in the latest study.