Background and Objectives: In adolescents and young adults, multiple studies have identified sexual activity and behaviors as significant risk factors for acquiring both human cytomegalovirus (HCMV) and hepatitis B virus (HBV). However, there are no reports on the prevalence or risk factors for infection of these viruses and hepatitis C virus (HCV) in an adolescent population with sexually acquired HIV. Goals: To examine the seroprevalence and risk factors of HBV, HCV, and HCMV infection in a population of HIV- infected male and female adolescents and in an age- and risk behavior-matched HIV-uninfected cohort. Study Design: A cross-sectional analysis of HBV, HCV, and HCMV infections in a cohort of HIV-infected and HIV-uninfected adolescents. Results: Adolescent males infected with HIV were more likely to have evidence of HBV and HCMV infection than HIV-uninfected males (23.7% versus 0%, respectively, for HBV, P = 0.008; 79.7% versus 50%, respectively, for HCMV, P = 0.004). HIV-infected females were more likely to have evidence of HCMV infection (78.5% versus 61.4%, P = 0.003) than HIV-uninfected females. No significant difference was found for HBV infection in the two groups of females. The rate of HCV infection (1.6%) was too small to make comparisons between the groups. To determine whether the differences in infection rates for HBV and HCMV could be explained by factors other than HIV status, a variety of possible risk factors were examined using univariate and multivariate analyses. A significant risk factor for HBV and HCMV infections for males was a homosexual or bisexual orientation. For females, a risk factor for HBV infection was having more than 10 lifetime sexual partners; for HCMV infection, HIV infection was the only risk factor. In addition, in the HIV-infected cohort, 15% of females and 36% of males who were seropositive for HBV had evidence of active HBV infection. Conclusions: These results emphasize the need for continued development of primary and secondary prevention programs and clinical screening and treatment for HBV and HCMV in adolescents.