Schoolwide effects of a multicomponent HIV, STD, and pregnancy prevention program for high school students. 
Few studies have tested schoolwide interventions to reduce sexual risk behavior, and none have demonstrated significant schoolwide effects.  This study evaluates the schoolwide effects of Safer Choices, a multicomponent, behavioral theory-based HIV, STD, and pregnancy prevention program, on risk behavior, school climate, and psychosocial variables.  Twenty urban high schools were randomized, and cross-sectional samples of classes were surveyed at baseline, the end of intervention (19 months after baseline), and 31 months afterbaseline.  At 19 months, the program had a positive effect on the frequency of sex without a condom.  At 31 months, students in Safer Choices schools reported having sexual intercourse without a condom with fewer partners.  The program positively affected psychosocial variables and school climate for HIV/STD and pregnancy prevention.  The program did not influence the prevalence of recent sexual intercourse.  Schoolwide changes in condomuse demonstrated that aschool-based program can reduce the sexual risk behavior of adolescents.