espite promise shown in the lab that the spermicide nonoxynol-9 may help prevent diseases like gonorrhea and chlamydia, the product appears to offer no benefit to women against sexually transmitted diseases, a new study shows.

The researchers, writing in the current issue of The Journal of the American Medical Association, said the infection rate was about the same among people who used condoms plus the spermicide and those who used condoms alone.

"It's not going to protect you from getting an S.T.D. or H.I.V.," said Dr. Barbra A. Richardson, a University of Washington biostatistician, who wrote an editorial accompanying the article.

Researchers should turn their attention to other microbicidal products, Dr. Richardson said, to see if they offer women more protection — at least until vaccines can be developed.

Nonoxynol-9, the most commonly used spermicide in the world, has been shown to kill sexually transmitted viruses in laboratory tests.

For this study, researchers from Family Health International, an agency in Durham, N.C., looked at 1,251 women being treated at 10 clinics in Cameroon, in West Africa. Half the women were assigned to use condoms and nonoxynol-9, with the other half using just condoms, and then researchers tested them six months later for disease. The chlamydia-infection rate was found to be same in each group, while the gonorrhea rate was 50 percent higher in the group that used nonoxynol-9.