We will conduct the study in two waves. For Wave One, we will randomize 10 alternative schools (5 to intervention and 5 to comparison conditions), and then recruit and enroll a cohort of 500, 9th-grade students into the study (cohort 1). For Wave Two, we will cross-over the treatment conditions among the schools and enroll a new cohort of 9th-grade students into the study. Prior to the intervention, we will conduct a baseline measurement and conduct a post-intervention measurement at 6-, 12- and 24-months. The major hypothesis to be tested is that adolescents attending alternative schools who receive a multi-component HIV/STD intervention will reduce levels of unprotected sexual intercourse relative to those in the comparison condition. The major dependent variables are unprotected sexual intercourse, number of sexual partners, and proportion currently sexually active (last 3 months).