Once upon a time the stereotypical publicist for a nightspot was a fat, balding old man who wore checkered suits and smoked cheap cigars. He slapped the backs of free-spending customers and bought bourbon for columnists he thought might plug his place of business.

Once upon a time was long ago, as the five women pictured here prove. Quietly, these women -- all less than 30 years old -- are becoming the mouthpieces for some of Washington's flashier bars, clubs and discos. When you read about a bar in a newspaper, or receive an invitation to a special function at a particular disco, or hear about an establishment from a friend, chances are it's because of their efforts.

From left to right, the women pictured are Linda Roth, 25, formerly with Tramp's, currently with the about-to-open Polo Club; Denise Cantwell, 25, of the newly opened Images; Carol Posnick, 27, of The Cellar Door; Patricia Wack, 23, of Tramp's; and Gliere Pratt, 25, of The Buck Stops Here.

It's their job to create an image for their club or disco or bar to bring in the "pretty" people, the upwardly mobile, affluent, attractive customers whose patronage means profits in the fickle world of Washington bars.

"It's entertainment. You're dealing with these people's leisure time and leisure dollars," says Linda Roth. "You want your club to be the top. It's show business."

Packing a room with spenders is a science, and the most important tool in Washington these days is a snappy mailing list. When Roth worked for Tramp's, she visited boutiques and modeling agencies to secure names of well-dressed, young handsome adults. They were invited to every special function the disco had.

For two months last summer Denise Cantwell worked to compile a list of 8,000 potential customers for Images.For two weeks she copied the names and addresses of doctors and dentists listed in the Yellow Pages with Northwest Washington addresses. She once worked as a waitress and had dated a bartender, so she was comfortable on the bar scene; for two months she drank spritzers and talked to people in bars, gathering more names. One person she met provided her with a mailing list of 1,500 trade association executives.

Gliere Pratt, like some of her cohorts, tries to crack the stewardess set on behalf of The Buck Stops Here. Airlines won't release the names and addresses of women who fly out of the Washington area, but some will agree to place invitations in the mailboxes of employes. The ploy is obvious: attract eligible singles of either sex, word will get around and you will have yourself a crowd.

For the Polo Club, Roth is calling on the friends of some of the financial backers of the new place.

"Can you imagine William Paley's address book?" she says almost breathlessly. The son of CBS mogul Paley is a backer of the Polo Club.

"We call people and get them curious," says Patricia Wack, who in addition to representing Tramp's will soon begin promoting a new saloon that will replace Billy Martin's Carriage House. "Then you call the press. People will read about you in the press and say, 'Ah ha, I know about that place, I've been contacted on that.' It's a one-two-three kind of thing."

"It's definitely well-thought out before we release an item to the press," says Roth. "Ear at the Star is daily, and if I need some press quickly, I'll call there. If I'd rather have an impact, or be more effective, I'll go with The Post." Or if it's specialized -- she recently suggested a story on how the Polo Club's food service will mesh with the Sheraton-Carlton Hotel in whose basement the club is located -- she'll phone a trade publication such as Nation's Restaurant News.

Not every newspaper or magazine, of course, makes use of the reams of publicity clubs send them. But if a particularly interesting party is covered by a reporter, the place in which it is held is usually mentioned. Or if a famous face does something of interest in a bar, the press person might call with the tip. A publicist lives for thos e mentions. It keeps the nightspot in the news, gives it a feeling of currency.

"You have to be able to be up all the time. You have to mask it when you're feeling down," says Wack.

"It's better if you're not married, because you work late at night," says Roth. "The problem is when there's a man who wants to see you on a regular basis; that's tough to do."

None of the five women interviewed are married. None of them expected to become publicity agents for nightspots. Roth graduated from the University of Maryland with a degree in communications. After a short stint on an Ocean City newspaper, she moved to Washington and began working at Tramp's.

Cantwell -- the middle child of a family of 11 who grew up in Queens -- arrived in Washington with modeling experience and a high school degree. After jobs in bars and clothing stores, she was hired to work at Images solely as a greeter at the front door. In the months before the club opened, her job description expanded to include compiling the club's mailing list, designing the staff uniforms and other nuts-and-bolts jobs.

Posnick booked acts while she was a student at the University of Minnesota, and two years ago began doing the same thing for The Cellar Door. If an act is unknown but talented, she'll contact editors at Washington papers to suggest stories. When Bruce Springsteen came to town, he'd done very little television, but he expressed an interest in talking on a Washington station. Posnick placed him on the television evening news.

Wack has a business management degree from the University of Maryland. She thought she'd grow up to be an accountant but moved from working in the couture department of Neiman-Marcus to flacking for Tramp's.

Pratt majored in psychology at George Washington University, sold Florida land and worked in sales for a health spa before joining The Buck Stops Here. She has handed out fliers on the street and mediated conflicts between the waitresses and bartenders at meetings that sometimes lasted until 6 in the morning.

Salaries for the women are in the middle or high teens. The hours are long. An empty room or a declasse crowd can induce bouts of depression. Sometimes bosses or staff are obstinate. When a place prospers, the owners get the glory. The irony of a publicist's job is not lost on them -- it's rare that their names ever make print.