The D.C. Office of Human Rights, in response to complaints of discriminatory hiring practices by restaurants, plans to launch next month a study of the sexual composition of restaurants' staffs in the city, according to the agency's director.

"Among the leading restaurants in town, other than cafeterias and lunchrooms, probably you would find 80 percent of the work force is male, and there are few opportunities for waitresses, except in the hotels," said Anita Bellamy Shelton, director of the office.

She said the office will make a general survey of restaurants' employes and take an in-depth look at certain staffs. Complaints could be filed against restaurants found discriminating, she said.

The office had planned a similar study in early 1981 but canceled it because of lack of manpower, said John Watkins, an agency spokesman.

An independent study of racial discrimination by restaurants is being done by the Hotel and Restaurant Employees Union Local 25. Ron Richardson, the local's executive secretary-treasurer, said he expects the union will file complaints with the human rights agency against some restaurants. The human rights agency's study will also examine racial discrimination.

Richardson echoed Shelton on hiring practices, saying: "I think if you go into . . . any of the really big-time restaurants, you would probably find no waitresses." The owners and managers seem to believe "waiters denote a higher class of restaurant. That's baloney," he said.

But John S. Cockrell, executive vice president of the 1,100-member Restaurant Association of Metropolitan Washington, said he didn't think hiring discrimination was a prevalent problem. "I really don't know of any place that says it only hires waiters because they want only men to wait on customers," he said.

Nearly two years ago, at a forum on waitress rights, Shelton called the city's restaurant industry one of the most flagrant abusers of civil rights.

Today, she said, her charge remains true. "Restaurants are still at the hub of discrimination in this town," she said.

Of 383 cases the Office of Human Rights closed in the fiscal year that ended Sept. 30, 71 were discrimination complaints filed by waitresses and other restaurant workers, Watkins said. Of the 71, 31 were settled, 32 found to be without cause and eight dropped, he said.

Belief that discrimination is widespread in the restaurant industry also has prompted the Women's Legal Defense Fund, along with other local groups, to prepare a handbook detailing employment rights of waitresses and other restaurant workers. The book will be published as soon as funding is obtained, a defense fund spokeswoman said.

Publicizing waitresses' rights is vital because "most women have, at some point in time, been a waitress or know that if worse comes to worse, they could fall back on waitressing," said Donna R. Lenhoff, the defense fund's associate director for legal policy and programs.

Although women's rights activists and union and District officials contend that discrimination is a prevalent problem among restaurants, restaurant owners disagree.

Dorothy Dee, a spokeswoman for the National Restaurant Association, said discrimination generally is not found in the food service industry. "Undoubtedly it can occur on an individual basis, but that's just like any other industry," she said.

Vito Zappala, a co-owner of Gary's Restaurant, 1800 M St. NW, said the city's more expensive restaurants tend to have only waiters, but it does not indicate discrimination. He said that although Gary's now has only men waiting tables, in the past it has employed women for the job.

Garth Weldon, manager of The Prime Rib, 2020 K St. NW, which does not have waitresses, said, "It's true that the trend in the fine restaurants is to have men in tuxedos waiting on tables." He said didn't know of any fancy restaurants on K Street that did have waitresses.

"We would like to hire women to do it. But one of the problems is that there's a certain amount of background needed," Weldon said. "It's somewhat of a Catch-22 situation. You want to hire people who have worked in the best places. There are very few women who have that in their family or background."

Nationally, nearly 90 percent of the 1.5 million persons who waited on tables in 1981 were women, according to the U.S. Bureau of Labor Statistics. Local figures are not available, but Richardson estimated 65 percent of his union's 10,000 members are women. He said the union represents workers at most District hotels and about 10 percent of the city's restaurants.

Although women make up the bulk of the restaurant industry's employes, the Bureau of Labor Statistics reports that full-time waitresses in 1981 had a median weekly income, including tips, of about $144, while waiters earned about $200.

Lauren Taylor, the Women's Legal Defense Fund's community education coordinator, blamed the waitresses' lower income partly on restaurants' hiring discrimination. "Women don't get the good-paying jobs in the fancier places," she said.

Another factor for the lower earnings is that some restaurants have women work during lunch and men during dinner, when higher menu prices generally mean larger tips, or have waiters work dining rooms while waitresses are kept to the restaurants' bars, she said.

Jody Sweeney of Northwest Washington considers herself a victim of such discrimination. She worked for a Capitol Hill restaurant that kept her and other waitresses in the saloon while waiters worked the dining room, where they earned up to three times as much in tips. After her boss refused to allow her to work in the dining room, she filed a complaint with the D.C. Office of Human Rights alleging sexual discrimination.

The agency found "probable cause" of bias, and the restaurant settled the case by paying Sweeney an undisclosed sum and allowing waitresses to work the dining room. The restaurant denied any wrongdoing. As part of the settlement, Sweeney agreed not to identify the restaurant.

Sweeney, 25, now a massage therapist, said she finds satisfaction in causing the restaurant to change its policy. "We've put employers on notice that this is the 1980s, that we're not going to step down on the rights that we have won," she said.

Other common problems the activists and officials say waitresses face are firings due to pregnancy, sexual harassment, demands for sexual favors by customers, co-workers or supervisors, and, in some instances, the types of suggestive uniforms some of them have to wear.

Some restaurant owners have fired pregnant waitresses out of a paternal feeling the women shouldn't work in such condition. But Taylor said, "You cannot treat pregnancies any different than you treat those with a temporary disability."