Objectives. The purpose of this study was to determine whether high school-aged virgins engage in sexual practices that can transmit sexually transmitted diseases, including the human immunodeficiency virus (HN). Methods. Data were collected from an anonymous self-administered survey of 2026 urban students in 9th through 12th grades. Results. Forty-seven percent of adolescents were virgins (42% of male adolescents and 53% of female adolescents). Of those who were virgins, 29% and 31% reported that, during the prior year, they had engaged in heterosexual masturbation of a partner and masturbation by a partner. respectively. The corresponding rates for heterosexual fellatio with ejaculation, cunnilingus, and anal intercourse were 9%, 10%, and 1%. Homosexual sexual activities were rare. Condom use for fellatio was also rare. Level of risk of virgins' sexual activities was associated with illicit substance use and other nonsexual risk behaviors, even after demographic variables had been controlled. Conclusions. Few high school-aged virgins engaged in anal intercourse, but many engaged in other genital sexual activities. Some of these activities can transmit disease, and all can indicate a need for counseling about sexual decision making, risk, and prevention.