The need for woman-controlled barrier contraceptives that protect against both bacterial and viral sexually transmitted pathogens is widely recognized [1±7]. In the absence of an effective vaccine or treatment, contraceptive methods capable of preventing sexual transmission of HIV as well as other sexually transmitted diseases (STD) are vital for protecting the health of women. Moreover, widespread violence against women, double standards of sexual behavior, and the imbalance of power in many sexual partnerships make methods initiated and controlled by women critically important. These issues may severely limit existing options for protection among women who cannot negotiate sex with their male partners without being accused of cheating, of beingloose'women, or of accusing their partners of infidelity [3, 4].

Vaginal microbicides (topical chemical barriers that protect against acquisition of a variety of STD pathogens, including HIV) may provide such alternative woman-controlled methods. Compared to male and female condoms, microbicides are expected to interfere less with intimacy and sexual pleasure, and be more discrete. Because detergents like nonoxynol-9 (N9) are microbicidal as well as spermicidal, several existing N9 contraceptives have been tested in observational and