The contraceptive failure rate of condoms varies from 2 to 13%, depending on the study population, yet it is the contraceptive method with the greatest capacity to protect against sexually transmitted diseases (STDs) and AIDS. Breakage and slippage during intercourse are important causes of failure, and individual behavior leading to consistent and correct use is the most important factor in condom effectiveness. Female-controlled barrier methods may actually prevent more STDs than condoms, because of their more consistent use. Using the diaphragm continuously and without spermicide was well accepted and effective in preventing pregnancy in one study. The female condom appears to have a contraceptive effectiveness close to that of other vaginal methods. It is likely that it also protects against STDs and AIDS. Nonoxynol-9 appears to have a protective effect against some STDs and the data concerning the protective effect of spermicides containing nonoxynol-9 against HIV is conflicting, yet suggests some protection, especially if products are used with relatively low frequency that avoids dose-dependent vaginal irritation. New spermicides which could also protect against viral infection without affecting epithelial cells are currently being studied