LeRoy Jeffers, a Houston attorney, stood up before the American Bar Association's policy-making House of Delegates Wednesday and thundered. "The future of this profession is at stake."

He wasn't talking about overcrowded court dockets, the proliferation of lawsuits or an excess of lawyers in the country - issues that Chief Justice Warren Burger feels are crucial to the legal profession. Nor was he talking about legal fees that are so high that many middle-class Americans can't afford to hire a lawyer - a problem that many think should tackled by the ABA.

Instead, Jeffers and his fellow delegates spent most of the ABA's 100th annual convention, which ended her Wednesday, worrying about the Supreme Court decision tha gave lawyers the right to advertise for the first time in 69 years.

Rather than dealing with some of the major problems facing the profession, the ABA convention focused on a narrow issue that hits lawyers in their pocketbooks.

Behind all of the claims that lawyer advertising will weaken the profession - one delegate, Burton Young of North Miami Beach, said, "It will destroy the nobility of our profession" - lies the fear that it will drive down prices for the bread and butter of most of the nation's 400,000 lawyers - simple wills, divorces, bankruptcies and incorporations.

This has already begun to happen, said Doris Jonas Freed, a divorce lawyer from New York City and secretary of the ABA's family law section. Before the June 27 Supreme Court ruling. New York lawyers charged $750 and up to handle an uncontested divorce case, she said, but now many lawyers' fees for a divorce have dropped to between $150 and $250.

Advertising is vital to the survival of legal clinics that are springing up around the country because it allows them to get the volume that results in cutrate prices.

It is also important to young lawyers trying to get their start. Establishment attorneys and large corporate firms are not expected to advertise; their clients learn about them through other means.

Because of its preoccupation with the issue of advertising most of the ruling powers of the ABA ignored troublesome issues looming for the future of the organized bar.

Joe Simms, deputy assistant attorney general of the Antitrust Division, warned the attorneys that they face the possibility of being charged with antitrust violations for many of their practices - including controlling who can be admitted to practice law, certifying lawyers as specialists, attempts to limit what nonlawyer assistants can do and determining who is authorized to practice law and who is not.

Simms said all these bar activities have "a significant anticompetitive attack."

Underscoring Simms' speech was a statement by Stephanie W. Kanwit, director of the Chicago regional office of the Federal Trade Commission, who said her agency is watching professional groups such as the ABA to help protect consumers from possible anticompetitive practices.

But even more disturbing was a panel of leading businessmen - the people who hire the lawyers whose annual income runs to five and six figures. They complained about the high cost and the value of the legal advice they received, and one businessman, Lester Pollack of C&A Financial Corp. predicted that businessmen "will seek legislation or regulation" to control legal fees.

Richard L. Thomas, president of the First National Bank of Chicago, said his bank's legal cost increased three times faster than its net income during the last five years.

There were other indications that the ABA's influence may be waning. For instance, no Supreme Court justices were present here - the first time in the memory of many longtime ABA convention-goers that this has happened.

Nonetheless the ABA is still one of the most influential professional associations in the country, probably far more powerful where it counts than, for example, the American Medical Association.

The ABA's real power comes from its small specialty groups whose members often shape the law that they have to deal with. The tax and antitrust section for example, are crucial for the passage of any legislation in those fields.

Their members are often called to Washington by government officials and members of Congress for informal advice. A congressional aide said ABA approval of grand jury revisions was crucial to getting a bill through Congress.

Perhaps the most publicized and influential activity of the ABA comes during the selection of a new Supreme Court justice. The seal of approval of the ABA's small but influential judicial selection committee is almost a necessity before a President will nominate a new justice. As an indication that this group is trying to become more representative, it named its first woman member - Washington attorney Brooksley Landau.