In the 25 years since the pill was introduced, millions of dollars have been spent searching for a drug that would allow men to share the risks, routine and responsibility of birth control.

Among the directions the search for the "male pill" is taking:

* Researchers have found some drugs that disrupt the production of LHRH, or leutinizing hormone-releasing hormone, a brain chemical involved in reproduction. The drugs inhibit sperm production, but they also abolish sexual desire. They are seeking ways to inhibit sperm production without affecting sex drive. Injections of male hormones may to do the trick.

* Doctors studying an infertility epidemic in rural China in the 1970s traced the problem to eating raw cottonseed oil. When the oil was withdrawn, fertility returned. Since then, more than 10,000 Chinese men have been involved in tests of gossypol, a pigment in cotton seeds that inhibits sperm production without destroying sex drive. It is taken in pill form.

Side effects of gossypol may include a drop in blood potassium levels, which can lead to irreversible muscle weakness and paralysis. Research is currently focused on whether smaller doses of gossypol reduce the toxic effects while still inhibiting sperm production. Chemists are also trying to produce a synthetic gossypol.

* Some researchers are seeking a vaccine that would inhibit sperm production. Research, still in preliminary stages, is geared to producing a vaccine, reinforced by periodic "booster" shots, that would maintain infertility until the boosters were stopped.

All methods have promise and serious drawbacks. None will be on the market soon, said Dr. Gabriel Bialy, chief of the Contraceptive Development Branch of the National Institutes of Health.

But whatever form the "male pill" takes, couples will have to cooperate for it to be effective.

"It will take a special relationship for use of the male pill," said Dr. Sheldon Segal, director of the Rockefeller Foundation's Center for Population Sciences. "It is the female who gets pregnant . . . If [the man] forgets to take his pill, he says, 'Gee, I'm sorry.' But she's the one who is pregnant."