Purpose: 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. Methods: 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. Results: 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 <= .001), indicating a more permissive attitude. Conclusions: Exposure to Internet pornography has potential implications for adolescent sexual relationships, such as number of partners and substance use. SEWs can serve an educational purpose and create an opportunity for adults to engage adolescents in discussions about sexual health and consumption of Internet material. Longitudinal research is needed to evaluate how exposure to SEWs influences youth attitudes and sexual behaviors. (c) 2009 Society for Adolescent Medicine. All rights reserved.