The nation's largest society of psychologists today will consider a resolution aimed at discrediting the controversial practice of using psychological therapy to try to convert homosexuals into heterosexuals.

The effort by the American Psychological Association to severely restrict the circumstances under which it would be ethical to practice "reparative therapy" has the support of many medical and professional organizations, and is in keeping with the association's 1973 resolution that homosexuality is not a mental illness. But the new proposal is vehemently opposed by a vocal minority of psychologists, psychiatrists and religious groups.

A more strongly worded resolution that would have deemed such therapy plainly unethical failed to pass muster at an APA convention two years ago, as did a similar resolution proffered by the more conservative American Psychiatric Association in 1994. The 1994 meeting was disrupted by demonstrators who said they had been successfully converted from gay to straight and didn't want others to be denied that opportunity.

The new effort by the Washington-based psychological association, which represents more than 151,000 researchers, educators and clinicians, stops short of declaring reparative or "conversion" therapy unethical and so is considered likely to pass, psychologists on both sides of the issue said. At the same time, it lays out principles that the organization hopes will stem the practice, which has been criticized as bigotry posing as science and by some accounts is being applied to hundreds of gay or bisexual individuals every year as part of an offensive by the religious right.

"In the past 10 years, Christian fundamentalists have enlisted a coalition of old-style psychologists, psychiatrists and social workers who have become very visible in this country and internationally, and who have as a mission to 'help' homosexuals get rid of their sexual orientation," said Doug Haldeman, president of the APA's society for the psychological study of lesbian, gay and bisexual issues, who helped craft the resolution being voted on today by the APA's council of representatives in Chicago. "Our aim is not to try to stop them per se or interfere with anyone's right to practice [therapy]," Haldeman said, "but we want to expose the social context that creates this market."

Specifically, APA officials said, the group wants to make sure that people considering such therapy are not being coerced by family members, employers, fellow church members or others.

"The question is, are you going into this knowing that homosexuality is not a mental illness, and knowing that you do not necessarily have a problem, and knowing that people who are gay and lesbian can demonstrate perfectly normal mental health?" asked Robert Pollard, a clinical psychologist and assistant professor of psychiatry at the University of Rochester.

Critics yesterday lambasted the proposal and assailed the underlying presumption -- supported by both the APA and the American Psychiatric Association -- that homosexuality is not an illness.

"It is a very serious resolution cloaked in lamb's wool . . . an attempt to brainwash the public," said Charles W. Socarides, a New York City psychiatrist and president of the National Association for Research and Therapy of Homosexuality (NARTH), based in Encino, Calif., which advocates reparative therapy.

"Homosexuality is a psychological and psychiatric disorder, there is no question about it," Socarides said. "It is a purple menace that is threatening the proper design of gender distinctions in society."

There are no official figures on the number of people who have tried reparative therapy. Exodus International, a Seattle-based Christian organization whose prime mission is to help people become heterosexual, gets calls from more than 500 people every month and has more than 6,000 people in therapy at its 90 ministries across the country, said Bob Davies, the organization's North American director, who counts himself among the successfully converted.

The APA said it has no idea how many others may take the secular route of getting conversion counseling with a licensed psychologist or psychiatrist.

Even less is known about how effective — or harmful — such therapy may be. Advocates say they have many examples of people who have been successfully converted and lived happily and heterosexually ever after. Critics claim that in most cases the therapy does not work and in many cases it amplifies a homosexual person's feelings of alienation. No studies on the topic have been published in peer-reviewed journals.

In the 1960s and early 1970s, professionals used "aversive therapies" such as shock treatments or nauseating drugs in an effort to induce changes in sexual preference. More recently therapists have turned to psychoanalytic techniques, with the presumption that homosexuality is the result of improperly formed relationships between parent and child.

The APA resolution affirms four basic principles with regard to reparative therapy, including the importance of obtaining "informed consent." An APA summary says that includes a full discussion of the potential for happiness as a homosexual, the statement that there is no sound scientific evidence that the therapy works, raising the possibility that therapy may exacerbate the client's problems, and an analysis of the client's true motivation for wanting to change.

Joseph Nicolosi, an Encino, Calif., clinical psychologist who is an APA member and executive director of NARTH, called the principles "intimidating and discouraging. It's like having a restaurant and having a big sign in the window saying, 'You might be poisoned, you might not be happy with the food.' "

Robert H. Knight, director of cultural studies at the Family research Council, the conservative think tank headed by religious activist Gary L. Bauer and one of the leading advocates of reparative therapy, blasted the resolution. "I'd like to know if the APA will require therapists to tell patients that there are strong cultural and religious reasons for saying homosexual sex is wrong," he said.

But others applauded the resolution. "These therapies amount to nothing more than psychological terrorism and are usually performed by practitioners who harbor intense bias against gay people," said David M. Smith, senior strategist for the Human Rights Campaign, the nation's largest gay and lesbian lobbying group.