Some, including several African leaders, have criticized the act’s emphasis on abstinence because of concerns that it further stigmatizes HIV infection by implying that it is due to a moral failure and because it may not be an effective means of HIV prevention. Are there data to show that programs that advocate only abstinence decrease HIV incidence? A meta-analysis suggested that “abstinence education” actually increased the likelihood of pregnancy in teenagers.8 In 5 studies, the risk of pregnancy in the abstinence-educated young women was 1.46 times greater than the control group and in the partners of abstinence-educated young men, 1.49 times greater. A randomized controlled trial in 659 African American adolescents compared 2 counseling interventions intended to change sexual behavior: 1 advocating abstinence and the other advocating safer sex by condom use. Controls were counseled about health unrelated to sexuality.9 Compared with the control group, the abstinence group reported less sexual intercourse at 3 months but not at 6 or 12 months. Conversely, compared with the control group, the safer sex group reported more condom use at 3, 6, and 12 months. Perhaps not unexpectedly, abstinence was most effective for sexually inexperienced participants, while safer sex was more effective for those who were sexually active before study entry. In other words, the efficacy of the interventions was different in different groups. Finally, analysis of the Uganda ABC experience suggests that the “be faithful” message, not the abstinence message, was the most effective aspect of the program.10 These data suggest that politics and ideology, and not science, may be driving the insistence on abstinence-only prevention mandated by the act. This lack of attention to the science may jeopardize the efficacy of US HIV-prevention efforts.