Ten years ago the nation's cities were burning and its campuses were in ferment with antiwar protesters. It was a sellers' market for law school graduates, and the best of them pressured major law firms into giving them time to take on public interest cases for free.

That no longer appears to be true. Interviews with law school professors and lawyers from around the country show that recent law graduates, coming out of a less socially-conscious mood on campus and facing and uncertain job market, no longer push law firms to increase their pro bono - for free caseload.

"The fad from pro bono is certainly gone," said Jane McGrew, a partner in Steptoe & Jahnson.

In its hayday during the late 1960s and early 1970s, the nation's courts were filled with eager young lawyers taking time out form their big money practices to represent the underdogs. They took cases on behalf of accused criminals who couldn't afford lawyers the mentally ill; alcoholics; draft resisters, and civil rights and antiwar activits. In the process; they helped important new principles of law.

Charles Halpern, for instance, as a young associate with Arnold & Porter, forced the courts to make sure patients they committed to mental hospitals in criminal cases are actually treated, not just locked up. And Peter B. Hutt, as an associate with Covington & Burling, won a landmark case that gave alcoholics the right to treatment instead of being tossed into police drunk tanks night after night.

Although some Washington law firms have continued their pro bono activities, other have dropped them. But the concept of public interest law has become institutionalized.

Halpern, for example, quit Arnold & Porter to direct the Council for Public Interest Law, and there are dozens of legal organizations that represent such diverse issues as the enviroment, women, Indians, blacks and Mexican-Americans, for example.

"Pro bono is becoming part of the system," said Lawerence H. Mirel, who joined a law firm in the late 1960s that takes a high percentage of public interest cases.

"More lawyers are doing pro bono now than 10 years ago," added Sara Ann (Sally) Determan, a partner in Hogan & Hartson who runs its Community Service Department.

"I think the kids were screaming in law schools 10 years ago because they had no outlet." she said. Now they don't she said, citing the neighborhood Legal Services Program, public defenres and enviromental groups.

"I don't have a feeling there is such a fall out of interest as alternate means."

There is a split among major law firms. Many continue and encourage pro bono activity, with the pressure coming from the partners, instead of the young lawyers, and as a response to outside criticisms of the profession. Other firms, however, have dropped most of their pro bono activities when the pressure from young lawyers ended.

Generally, those firms that have continued pro bono work are willing to be identified while those that have dropped out have asked that their names not be used.

"It's fallen off," said a partner in a major New York-Washington firm. "It doesn't seem to be a hot issue any more," said a partner in another firm. "We used to have a pro bono committee, but it has fallen into disuse."

"There's no question," said Arnold & Porter's Stuart Land, "the intensity of the commitment to pro bono is not as great as it was during the late '60s when everyone was undergoing an identity crisis."

Nonetheless, he continued, for some firms, including his own, pro bono work has become a permanent activity. "I think all of those firms have some definite pro bono structure whereas a year ago it was catch as catch can."

Hogan & Hartson, for instance, set up a special community service department to handle pro bono cases the same way it had a tax department to take cases in that area.

The firm hired John M. Ferren, now a D.C. Court of Appeals judge, from Harvard to run that department. He was succeeded by David S. Tatel, who is now head of the Office of Civil Rights of the Department of Health, Education and Welfare.

Determan, who left her tax practice to take over the department when Tatel went to HEW, said her firm uses its community service activities as a selling point when it rises to attract the brightest law students from the best schools.

he commitment in time and money is great. On one case alone, representing the NAACP in Mississippi, Hogan & Hartson contributed services during the past 18 months that would have cost paying clients $150,000.

Convington & Burling assigns two lawyers, two paralegals and two secretaries to a Beighborhood Legal Services Program office in Washington as a regular commitment.

In addition, the firm represents a group of journalists and historians who want access to Henry Kissinger's as former congressman Otto Pass-man's secretary because he said he wanted a man for the job.

It's harder now than it was 10 years ago to break new legal ground in civil rights, discrimination or environmental law.

"In the early days it was like picking diamonds off the field. It was easy," said Mark Green of Ralph Nader's Congress Watch.

"We're on second-and third-generation issues for the most part," added Determan, whose firm is working in one of the few areas where new ground is left to be broken by representing the Mexican-Amercian Legal Defense and Education Fund in trying to win voting rights for Spanish-speaking Americans.

Moreover, she continued, recent decisions by a more conservative U.S. Supreme Court have made federal court suits less attractive for social interest cases while the first Democratic administration in eight years makes it easier to achieve gains through the executive and legislative branches.

All this has contributed to what appears to be a downturn in the amount of pro bono work by major firms.

"The David and Goliath image is changing a little bit. That's partly why it has lost some of its appeal. The image of a lone lawyer, a Ralph Nader, striding in there and picking off the giants is no longer there," said Mirel.

Not all partners in major firms agree that lawyers should contribute time - which means money - for non-paying public interest cases.

Halpern recalled that one partner at Arnold & Porter, which maintains a great commitment to pro bono work, would regularly stop him in the hall to ask. "Did you bill any hours today? Those were jokes, but they gave you a message too.

At Hogan & Hartson, the community service department was sold to some more conservative firm members as an aid to recruiting the best young lawyers.

"For every case we take," said Covington & Burling's Peter Hutt, "there is a partner in the firm who thinks we are absolutely nutty, and I hear from them.

"I tell them it's not my job to say whether a case is right or wrong. My job is just to say it's an important issue that we should get into, or if it's not an important issue that there are no conflicts of interests."

Conflicts are the biggest barrier to major firms taking pro bono cases. Alan B. Morrison, of Ralph Nader's Public Citizen Litigation Group, recalls trying to place a nuclear power case with a firm but being turned down because they were seeking clients in the industry.

Nader complained that the big firms are willing to take civil rights and employment discrimination cases, but refuse to deal in economic issues and issues that would make regulatory agencies more responsive to the public.

"They won't do that because that would hurt them." said Nader.

Arnold & Porter's Land, however, thinks those cases should be pushed by public interest law firms to avoid conflict of interest problems. Among other things, he said, it hurts a firm tactically to take a legal position on behalf of a pro bono client that can be used against it when it argues for a paying client.