Soon after the AIDS epidemic first was recognized in 1981, it became clear that penile-anal and penile-vaginal sex were primary causes of HIV spread and that safer sex practices (ie, abstinence, monogamy, consistent condom use, and substitution of less risky behaviors, such as oral sex) were protective against human immunodeficiency virus (HIV). These prevention approaches seemed effective as new HIV infections decreased from more than 100 000 per year in the 1980s to approximately 50 000 per year by the mid-1990s.1 Although early mortality among sexually active individuals infected with HIV explained some of the decrease, increased condom use clearly played a role.