A bisexual man gave AIDS to his wife before his death and the widow then infected a next-door neighbor before her death, providing clear-cut evidence of sexual transmission from women to men, doctors said today.

The cluster of cases "appears to represent a well-documented example of sexual transmission" of the AIDS virus "from a man to a woman to a man through frequent but traditional sexual practices," two Cleveland doctors reported in a letter to the New England Journal of Medicine.

"We believe the risk of such transmission is real and that sexually active heterosexual men and women should be aware of these data," said Drs. L.H. Calabrese and K.V. Gopalakrishna.

They told of a 37-year-old married bisexual man who traveled frequently between New York City and Cleveland from 1981 to 1983. He admitted to homosexual activity on his business trips and in 1983 developed symptoms of acquired immune deficiency syndrome.

His 33-year-old wife of 10 years initially appeared to be healthy. She reported having had regular vaginal intercourse, accompanied by heavy mouth kissing, with him twice a month before his death, but no other sexual contact. But 18 months later, she too developed an AIDS-related pneumonia and died.

Several months after her husband's death, she began an affair with a 26-year-old man who lived next door. The man reported that for about a year they had daily vaginal intercourse, accompanied by heavy mouth kissing. But he said there was no other sexual contact and that he had no history of homosexuality, drug abuse or contact with prostitutes.

He is now infected with the AIDS virus and shows signs of an illness that sometimes precedes the full-fledged disease.

The woman's 10-year-old daughter has no signs of infection, the doctors said.

The doctors' report comes amid continuing debate in the medical profession over the spread of AIDS in the United States from women to men. Although AIDS is known to be spread heterosexually in some African countries, most of the cases in this country have involved homosexual men and intravenous drug abusers. Some American studies have linked AIDS in men to sexual contact with female prostitutes or female drug abusers.

"Some people have felt that the evidence of transmission through vaginal intercourse is still not convincing because of the relatively few cases . . . . We believe that it does occur, but it may be uncommon," said Dr. Harold Jaffe of the federal Centers for Disease Control.

Jaffe said that of the 19,181 U.S. cases reported as of April 7, only 45 are listed as men who got the disease through heterosexual contact, most of them from drug-abusing sex partners.