Richard Rappaport found clients few and far between when he opened his Washington law office last November. But he began advertising two months later, and since then his practice has flourished to the extent that the 29-year-old lawyer now has branches in the Virginia and Maryland suburbs.

"Without advertising I think I would have starved the way friends of mine just starting did. I doubt I would still be existing. I certainly wouldn't have the clients I have now," he said.

Similarly, legal clinics - supermarket-type law firms that specialize in providing routine legal services at cut rates because they get a high volume of business - have multiplied across the country since the U.S. Supreme Court last June 27 struck down state and local bans against lawyers' advertising.

There were 20 of them before the Supreme Court ruling and "the last them we looked" - in December - there were 50 or 60 Clinics with more starting weekly, said Sandra DeMent of the National Resource Center for Consumers of Legal Services.

"Clinics could not exist without advertising," she said.

The Baltimore-based Legal Clinics of Cawley & Schmidt, for example, advertise regularly - including the use of TV spots. The firm has tripled its branches, from 6 to 18, in the past year and has spread into five other states from the Baltimore Washington area.

In Los Angeles, the Legal Clinics of Jacoby & Meyers have grown from 4 offices to 16 since last June. The firm advertises extensively and believes that its television commercial - which was picked by the magazine Advertising Age as one of the 100 best of last year - will attract 30,000 to 35,000 new clients this year.

While an American Bar Association survey this spring showed that only 3 percent of the nation's 450,000 lawyers had advertised since the Supreme Court ruling, the ABA believes young lawyers such as Rappaport and legal clinics are typical of those who do take out ads.

"Advertising gives an opportunity for a young lawyer to come into a new area and say, 'I am available in these specialities and at these prices.' Those are the people who would expect to advertise, and they are doing it," said Roger P. Brosnahan, a lawyer from Winona, Minn., who heads the ABA commission on advertising.

In his town of 40,000 people for instance, three former law clerks to district court judges, all strangers to Winona, formed a new law firm. They are the only lawyers to advertise, he said, and they are getting clients that way.

Moreover, there are strong indications from around the country that lawyer advertising is lowering the cost of everyday legal services - uncontested divorces, simple wills and personal bankruptcy cases, for example - as consumer advocates had hoped.

In Washington, the standard fee for the simplest divorce - uncontested with little property involved and no children - was about $350 to $500 five years ago, said the Rev. Raymond B. Kemp, head of the D.C. Bar's Citizen Advisory Committee. Now such divorces are being widely advertised at prices from $125 to $150, and one firm - Dobrovir, Oakes, Gebhardt & Scull - now advertises do-it-yourself kits for $75.

In Phoenix, the cost of an uncontested divorce dropped in the past year from $350 to as low as $125, said Van Osteen whose legal clinic brought the case to the Supreme Court that resulted in the landmark decision allowing lawyers to advertise.

"The savings are dramatic," he said.

"The inability to advertise kept prices artifically high."

Mitchell W. Miller, who advertises a bankruptcy clinic in Philadelphia, told the ABA Commission meeting here, "The competitive effect is apparent. This is beautiful for the public." And Brosnahan said commission hearings have shown that a reduction in legal fees followed the Supreme Court opinion.

But consumer advocate Ralph Nader complained that advertising is only reducing legal fees "on the level of the $145 divorce. It's not reducing the fees lawyer charge municipalities on bond issues" - one of the most lucrative areas of the law.

It is just these high-powered, high-fee lawyers who oppose lawyers' advertising and who refuse to advertise themselves. The ABA poll showed that 89 percent to the nation's lawyers say they will not advertise.

"It would appear there is a national reluctance on the part of lawyers to advertise," said Brosnahan.

Yet chinks in this reluctance are beginning to appear. Last month, for the first time, the Park Avenue law firm of O'Brien & Associates took a prominent display advertisement in New York Magazine headed, 'Everyone needs a lawyer - just in case!"

Serko & Simon, a New York firm specializing in customs and trade law, ran into trouble from the organized bar when it placed two advertisements that were far more eyecatching than the usual run of attorneys' ads. One of the ads showed a picture of a sunrise with the caption, "A NEW day has dawned for those seeking and providing legal services."

The Association of the Customs Bar, whose 130 members comprise almost all the lawyers in the country who specialize in customs law, referred the advertisements to its discipline committee "for possible disciplinary action."

Serko & Simon subsequently sued the Customs Bar in New York's federal court to block any possible such action. In the suit, believed to be the first by a law firm against an organized bar since the Supreme Court decision, Serko & Simon argued that any restrictions on its ads violate its constitutional rights.

The Supreme Court has left the formulation of specific regulations governing lawyers' advertising to the state high courts, which oversee the conduct of lawyers.

The ABA, at its annual meeting last August, recommended two alternate sets of rules, but the Justice Department said that neither met the Supreme Court's requirements. So far, an ABA survey shows about 25 states have enacted advertising rules, with about half of those enacted being less restrictive than the ABA recommendations.

In this area, Maryland passed one of the least restrictive codes in the nation, in effect allowing attorneys to adgertise anything that is not false or misleading. The D.C. Court of Appeals is considering a number of proposals, including one from the D.C. Bar that goes even further than the Maryland rule in that it allows soliciting. Virginia has as yet taken no action.

Across the country, lawyers who oppose individual lawyers, advertising are looking into institutional ads to drum up business for the whole profession. In Ohio, for example, the bar association set aside $550,000 for a two-year advertising campaign to encourage the public to use lawyers' services.

"There's a terrible paradox in the country," said Brosnahan. He cited an ABA study that showed that 70 per cent of the American people don't use a lawyer when they need one and then noted that at the same time law schools are graduating 30,000 lawyers a year, many of whom can't find jobs.

It appears that many of the fears voiced by opponents of lawyers' advertising about the evils of ads have failed to materialize during the past year. Washington lawyer David Scull, who does advertise, recalled that some mebers of a Maryland bar committee raised fears that law firms might hire Baltimore Oriole star Brooks Robinson to endorse them.

"Lots of horrors about false advertising apparently haven't materialized," said Linda C. Cawley, of the Legal Clinics of Cawley, Schmidt.

"While all the ads may not be tasteful to some people," added DeMent, "the ads have not been grossly misleading or wildly offensive."

According to Brosnahan, a new fear is developing among lawyers who practice alone or in small firms - about half the practicing lawyers in the country - that large firms will use their economic strength to conduct massive advertising campaigns and grab a greater share of the nation's legal business.

In fact it is the small firms and legal clinics that dream of using advertising to expand nationwide. Rappaport, the young Washington lawyer, said he plans to open a branch in Miami soon and expand to New York by the end of the year.

Similarly, the Legal Clinics of Cawley & Schmidt have talked about becoming the H & R Block of everyday law, with branches all over the country. Now they are franchising their name, systems and TV ads to lawyers in states such as New York and Tennessee.

"Advertising is 100 per cent responsible for our expanison," said Cawley.

Bruce Haupt, a Washington lawyer, said it has been virtually impossible to get divorce cases now without advertising. "You can't break into the field without advertising," he said.

Under pressure from the courts and the Justice Department, other professions are beginning to follow the lawyers' lead and relax restrictions on advertising.

The American Institute of Architects voted last month to permit "dignififed" advertisements by its members after the Justice Department threatened a suit. Earlier this year, the American Institute of Certified Public Accountants swept aside a 50-year ban on advertising. Dentists and some doctors are also advertising.