A quarter-century ago, the liberal cause was banning the bomb. Then it was civil rights and then ending the Vietnam war. Now there is human rights, a cause whose stylishness is the source of some mixed feelings among the organizations benefiting from the boom.

Several groups that doggedly worked to promote human rights for years before it was chic now report waves of new members, contributions, participation. They disagree over the reasons, crediting variously. President Carter's vocal championing of the cause or their own organizational work is paying off at last. They don't deny the new atmosphere.

"It's an OK thing to be involved in now," said Susan Montgomery of Washington, a part-time staffer for Amnesty International, as she held up one end of a banner denouncing alleged human rights in Indonesia during a recent minidemonstration.

"The growth in contributors is dramatic," acknowledged Amnesty International's U.S. noard chairman Whitney Ellsworth in New York, "but the growth in active volunteer workers is nowhere near as dramatic. We're trying to convert people into taking an active role."

Anmesty International, a 16-year-old, London-based organization, is one of the more spectular beneficiaries of the new public interest. From a June, 1975, contributing U.S. membership of 3,000, it grew to 50,000 by December, 1976. It has gained another 24,000 donors since then.

The Washington offices opened in June 1976 with three members. The area now has three independent "adoption groups" with a total of more than 120 active members.

Each "adoption group" is assigned three political prisoners, one each in an Iron Curtain country, a western nation and a nonaligned country. Each member of the group is asked to write one letter a month on behalf of each prisoner to the government concerned, an international organization, the prisoner's family or to some other relevant group.

Although 19 groups were closed down last year, including one in Alexandria, because their active membership had dwindled to one or two, the overall number of adoption groups rose from 85 in November, 1976 to 103 today, according to Amnesty's membership coordinator, Bob Maurer.

"People's energies were concentrated on ending the Vietnam war. Now they're into this instead," said artist Ann Dawson, former coordinator of the defunct Virginia Amnesty group who is no part of one of the growing Washington units.

Steve Klitzman, leader of one of the units, called that syndrome "post Vietnam emptiness. Some people have gone to the environmental movement, some are apolitical, but human rights now is home to a fair amount of idealism."

Some enthusiasts may be more idealistic than others.

"Anybody who has a cause of any sort of latcjes on to the human rights issue now, whether they're anti-communism, antiwar, antiforeign aid or whatever," said William Goodfellow of the Washington-based Center for International Policy, a human rights-oriented study group backed by the Fund for Peace.

With other administration critics, he worried that President Carter's brand of human rights had not been sufficiently defined to effect any real change.

"Hitler promises not to bake as many Jews this month and therefore President Carter's message has been heard," scoffed Sol Landau, acting director of the Transnational Institute, international arm of the Institute for Policy Studies. "To show improvement has tended to mean only abatement of whatever hideous process was going on . . . not necessarily any change in the process.

"That's making a mockery of what I'm sure is President Carter's sincere desire to see people treated decently," Landau continued.

The vagueness of the rhetoric enables all the adherents, including the Carter administration, to cast foreign affairs in their own lights, Landau said. He went on: "The question then becomes not how does Vietnam deal with the food shortage or the cripples left over from the war, but is habaes corpus functioning there? . . . It tends to make human rights into a cliche."

A grim aspect of the boom is that it wouldn't have happened if rights were not being increasingly violated, according to Eugene Stockwell, head of the overseas ministry of the National Council of Churches.

"We've been bombarded with requests from (groups in) country after country to do something, churches around the world asking for help in bringing the situation to the attention of the international community," he said, "as repression has grown, so have the efforts to counter it."

The Council this year opended a special Office on Human Rights, but did not find universal support for it among its member demominations, Stockwell said.

All the organizations are working to consolidate the new public awareness, whatever its depth or origin.

Amnesty International credits its direct mail campaign rather than President Carter's involment for much of its growth, which has occurred especially in the South and Midwest.

Amnesty press spokeman Larry Cox said the surge in worldwide interest predated Carter's election. He noted that Amnesty bends over backward to keep from being identified with the administration.

The group also worries, said board chairman Ellsworth, that human rights might become overly politicized.

The International Commission of Jurists,a much smaller organization made up of high-powered international lawyers and legions of student and other volunteer workers, is pleased with human rights boom.

"While there've been no tangible results, it has been useful at stirring interest and getting the word around," said E.W. Debevoise, board chairman of the American Association for the ICJ's official members, limited by rule to 38.

ICJ has noticed a sharp rise in requests for its periodic reports on the human rights situation in individual nations, most recently on Uganda, the Philippines and Iran, he said. The group receives contributions from 1,200 attorneys in the United States and has opened a membership drive.

The United Nations Association, linked to human rights promotion since Eleanor Roosevelt's involvement, reported a "definite growth in human rights sentiment" among its 30,000 members, according to David Dull, a special assistant in the organization. "We see it in the mail we get in the programs put on by the (more than 200) chapters," he said.

The Washington area U.N. Association has declined slightly in members, from 1,177 last year to 1,067 now, but human rights convern is more pronounced, said 2d vice president Dorothy Hazard.

The question now, the groups agreed, is whether the feeling will translate into permanent involvement at the citizen level and policy change at the top.