Mass media play an important role in the socialization of youth. Given its expanding nature and accessibility, the Internet may be at the forefront of this education. However, the extent of the Internet's impact on adolescent sexual attitudes and behaviors is not yet known. A total of 433 adolescents completed an anonymous survey at a health center in New York City. The cross-sectional survey assessed Internet accessibility, exposure to sexually explicit Web sites (SEWs), sexual behaviors, and sexually permissive attitudes. Of the participants, 96% had Internet access, and 55.4% reported ever visiting a SEW. Logistic regression analyses revealed that adolescents exposed to SEWs were more likely to have multiple lifetime sexual partners (OR=1.8, CI=1.2, 2.9), to have had more than one sexual partner in the last 3 months (OR=1.8, CI=1.1, 3.1), to have used alcohol or other substances at last sexual encounter (OR=2.8, CI=1.5, 5.2), and to have engaged in anal sex (OR=2.0, CI=1.2, 3.4). Adolescents who visit SEWs display higher sexual permissiveness scores compared with those who have never been exposed (2.3 vs. 1.9, p