This study evaluated All4You!, a theoretically based curriculum designed to reduce sexual risk behaviors associated with HIV, other STDs, and unintended pregnancy among students in alternative schools. The study featured a randomized controlled trial involving 24 community day schools in northern California. A cohort of 988 students was assessed four times during an 18-month period using a self report questionnaire. At the 6-month follow-up, the intervention reduced the frequency of intercourse without a condom during the previous 3 months, the frequency of intercourse without a condom with steady partners, and the number of times students reported having intercourse in the previous 3 months. It also increased condom use at last intercourse. These behavioral effects were no longer statistically significant at the 12- and 18-month follow-ups. The All4You! intervention was effective in reducing selected sexual risk behaviors among students in alternative school settings; however, the effects were modest and short term.