This paper reviews published research on school-based programs to reduce sexual risk-taking behaviors. Analysis of 23 studies of school-based programs supports several conclusions about these programs. About 93 percent of all high schools offer sexuality or human immunodeficiency virus (HIV) education, and the majority of these programs include the topics of abstinence, contraception, pregnancy, and sexually transmitted diseases, including HIV and acquired immunodeficiency syndrome (AIDS). There is broad public support for both sexuality education and HIV education. Research indicates that such programs do not hasten the onset of intercourse among students or increase its frequency. Four curricula have been identified as increasing the use of condoms or contraception among some groups of participants. The proportion of junior and senior high schools with school-based health centers is small but growing rapidly. Research indicates that effective programs implemented in U.S. schools can have an important impact on reducing sexual risk taking behaviors. Recommendations are made for additional funding for such programs and for teacher training and resource allocation. (Contains 66 references.) (SM)