The companion article by Rosenberg and Gollub in this issue summarizes data from 10 observational studies and concludes that female-controlled contraceptive methods, under typical conditions, are comparable to condoms in preventing sexually transmitted diseases and should be merchandized as such. While we agree that chemical and mechanical contraceptives provide protection against some sexually transmitted diseases, we think the authors have overstated the scientific case for these methods, especially in comparison with the condom. We think the current data remain inconclusive regarding the absolute protection of spermicides against the human immunodeficiency virus and their level of protection--relative to that of the condom--against other sexually transmitted diseases. Three reasons account for our differences: the limitations in the comparative data; the reported adverse effects of spermicides on vaginal conditions, including genital ulcers; and the relative value of condoms, even under typical conditions, in preventing sexually transmitted diseases. For these reasons, we would currently counsel both women and men who practice high-risk sexual behaviors to use condoms as their first line of defense. If this is unacceptable, the female barriers become a fallback position to protect against bacterial sexually transmitted diseases.