Barrier contraceptives, including mechanical methods, chemical methods, and combinations thereof, have the potential to decrease the spread of STDs, are inexpensive, and do not have any systemic effects. Currently, the concerns that the efficacy of latex condoms is limited because they are not consistently used, they can break, may cause allergies, and have a limited shelf-life has led to the development of condoms made of other materials such as polyurethane. Spermicides using nonoxynol-9 as their active ingredient have been shown to be effective in preventing the transmission of some STDs such as gonorrhea and chlamydia. In the absence of well-controlled studies of nonoxynol-9 efficacy against HIV, questions have been raised that some formulations, high doses, or frequent use may be associated with genital tract irritation, and possibly, enhancement of HIV transmission. Because heterosexual transmission will continue to be the major route of HIV transmission worldwide, the development and consistent use of a chemical or mechanical barrier during intercourse may be the best way to decrease the spread of HIV.