By today's standards, the ad seems staid, even timid. "Do you need a lawyer?" inquired Phoenix lawyers John Bates and Van O'Steen, promising "legal services at very reasonable fees."

The young lawyers' advertisement in the Arizona Republic for their legal clinic trumpeted no celebrity endorsements, no holiday-special discounts, but it drew the wrath of Arizona bar authorities. They accused the pair of violating a disciplinary rule, similar to that in force in almost every state, prohibiting lawyers from publicizing themselves through newspaper ads, radio or television announcements, or even display advertisements in the Yellow Pages.

That local disciplinary action ended up before the Supreme Court, in Bates v. State Bar of Arizona. In the view of many legal scholars, the decision handed down 10 years ago, on June 27, 1977, revolutionized the practice of law in this country more than any other Supreme Court decision in history.

Rejecting the warnings of the organized bar that freeing lawyers to compete in the "hustle of the marketplace" would "tarnish the dignified public image of the profession," the high court ruled 5 to 4 that lawyers have a constitutional right to advertise their services.

A decade later, advertising has become a way of life for many American lawyers. The practice of law has evolved into a more cutthroat, dollar-oriented business, a change due in large measure to the loosening of restrictions. And the debate outlined in the Bates case rages on.

Many lawyers are appalled at what they regard as the shameful spectacle of lawyers hawking their wares on billboards and matchbook covers. Retired chief justice Warren E. Burger has said he would "dig ditches" before resorting to advertising and bemoaned the marketing of legal services like "other commodities from mustard, cosmetics and laxatives to used cars."

Others -- even some officials of the legal establishment, which battled vigorously against the Bates result -- view advertising as a healthy unleashing of market forces that has cut the cost of basic legal services for many consumers, once befuddled about where to turn for legal help.

"I think it's been a good thing," said Thomas S. Johnson, an Illinois lawyer who chairs the American Bar Association Commission on Advertising. "It's opened the marketplace and has made lawyers more available to more people."

The changes wrought by Bates have touched almost every lawyer in America. Sole practitioners, finding their businesses squeezed by high-volume legal clinics with million-dollar television advertising budgets, may invest in a full-page spread in the Yellow Pages. Blue-chip law firms that once questioned whether it was unseemly for their lawyers to carry business cards now hire high-priced public relations consultants to develop marketing strategies and make sure their partners get good ink.

Bates, written by Justice Harry A. Blackmun, is "probably the single most important Supreme Court opinion afffecting the structure of the practice of law and the delivery of legal services," said New York University legal ethics expert Stephen Gillers. "In a way it seems like longer {than 10 years since the decision} because we've seen so much legal advertising.

In 1978, the year after Bates, only 3 percent of lawyers polled by the American Bar Association Journal reported advertising. By 1983, the ranks of the advertisers had climbed to 13 percent; two years later, 24 percent of lawyers said they advertised.

"It's a lot more than I expected," said Johnson. "At the time the decision was handed down it was about as popular as venereal disease with the bar leadership."

Today, lawyers invest millions of dollars in the war for the hearts, minds and checkbooks of potential clients. In 1978, lawyers bought $900,000 worth of television time, according to figures compiled by the Television Bureau of Advertising. Last year, that figure reached nearly $47 million.

In a 1983 study of the effect of advertising on the cost of legal services, the Federal Trade Commission concluded that fees for legal services such as wills, bankruptcies, uncontested divorces and uncomplicated accident cases were 5 to 13 percent lower in the cities that had the fewest restrictions on advertising.

"As advertising increases in the legal service market, prices will decline," said the FTC, which surveyed 3,200 lawyers in 17 states.

Advertising "forced lawyers to become more efficient," said Gail Koff, a founding partner of Jacoby & Meyers, a 150-office legal chain that is one of the country's heaviest advertisers. "In midtown Manhattan an uncontested divorce cost $1,500 13 years ago," she said. "Our fee now is about $500."

Others, including the president of the American Bar Association, suggest that clients may get inferior service from lawyers who advertise. "The best value will be found in the nonadvertising group of lawyers," said ABA President Eugene C. Thomas, a Boise, Idaho, lawyer. "The better services are being provided by whose who are not advertising. That's the reason why the others are advertising."

"I couldn't disagree with him more," responded Koff, whose firm spent nearly $5 million on television advertising last year. "Your attorney out there who is not advertising is basically taking as clients whoever he can get to come through the door and doesn't have the specialization behind him, doesn't have the system and support services that a large organization can offer."

Indeed, a 1979 American Bar Foundation survey of 74 Los Angeles residents found that the 22 who went to Jacoby & Meyers were more satisfied with their lawyers' services than the 52 who sought help from traditional firms.

A fraction of the advertising has met opponents' worst fears, bordering in their view on the tasteless or straying far over that line.

In one commercial for divorce lawyers, shown on local television, a whirring chainsaw cuts the couple's couch in half, then buzzes ominously over the family dog. A Wisconsin lawyer's television spot features him rising from the water to the strains of "Swan Lake," festooned with jewelry, to offer, "If you're in over your head because of inflation . . . . " In the District, the bar's legal ethics committee ruled that Ashcraft & Gerel's television commercial featuring Redskins running back John Riggins violated the bar's rules against testimonials. "Holiday special -- give that spouse of yours something he or she has been wanting for a long time -- a divorce," a Florida lawyer's ad urged.

"What kind of professional, or what can people think about professionals when they know . . . you're going to knock 10 percent off because it happens to be . . . a summer special?" Maryland State Bar Association President Vincent Ferretti Jr. asked at a hearing last year by the ABA Commission on Advertising.

Maryland District Court Judge Thomas H. Sisk Jr. told the same commission that Maryland lawyers "feel that some type of cheapness has pervaded the practice of law in Maryland, and they uniformly blame it on the distasteful advertising."

Advertising, he said, "has sucked the rural counties absolutely dry of personal injury cases" as clients turn to the city lawyers whose ads they see on television. Baltimore is one of the heaviest television legal advertising markets in the country.

Others assert, however, that the vast majority of legal advertising is quite respectable and dignified. "Every once in a while a schlocky ad appears and everybody gets upset, but that's rare," said Johnson, who heads the ABA advertising commission. "Ninety-five percent of it is dignified and there's been an enormous increase in the tolerance by other lawyers."

What once was shocking now seems acceptable. The American Bar Association's Standing Committee on Ethics permitted a lawyer to set up a tent at a state fair, complete with a sign outside that he would write wills on the spot.

"The bar would have reacted in horror years ago," said Georgetown University law Professor Samuel Dash, a committee member. "Today, we found that there was nothing really improper on that."

One state ethics panel passed on the ad of an attorney who billed himself as "The Lawyer Who Makes Housecalls." In Rhode Island, the state bar counterattacked with its own ads, warning potential clients not to choose lawyers simply because they advertise.

And enterprising lawyers have pushed the boundaries of Bates, entering such new advertising frontiers as "telemarketing," in which customers are called and asked if they want to join a prepaid legal services plan, a sort of legal version of health insurance, and direct-mail solicitation in which lawyers write, for example, to accident victims or their survivors to offer their services.

J. Anthony Clark, who has done work for Montgomery Ward's legal services plan, said he cringed when he discovered the group was telemarketing. "I said, 'There is no way you can do that. That is entirely unethical,' " he said. But after researching the issue, Clark said, he concluded that it would be permitted by the ethical rules in many states.

The elite firms of Wall Street and K Street may not have bought television ads, but they too have felt the impact of Bates. Many top law firms have hired public relations consultants who issue press releases heralding the firms' latest acquisition of big-name partners or urging reporters to call the firm's experts for quotes.

"Lawyers said, 'Well, I might not advertise in the conventional sense, but since it's permissible to do so I'm going to consider other ways to market my practice . . . that might be considered more dignified,' " Johnson said. "It is unlikely that would have happened if the Bates decision had not come down."

"The whole legal profession top to bottom has been forced to come into the 20th century," Koff said. "I think a great deal of that comes from the fact that lawyers have been allowed to advertise."