CONTEXT. Rigorous evaluations are needed to assess whether adolescent sexual health interventions have an effect on young peopled risk-related perceptions and behaviors. METHODS:A quasi-experimental design was used to evaluate the impact of adolescent sexual health interventions conducted by social marketing programs in Cameroon, Botswana, South Africa and Guinea in 1994-1998. The some statistical models, using data from baseline and postintervention surveys, were employed to study each intervention; the results are presented within the framework of the Health Belief Model. RESULTS. The interventions were associated with improvements in a variety of health perceptions among women, including perceptions of benefits of and barriers to protective behavior; for women, the interventions also had positive impacts on contraceptive use. Effects were much more limited among men, although evidence from Cameroon and Botswana suggests that men were less likely after the intervention than before to have multiple or casual partners. The Cameroon intervention, the most successful of the four, used multiple communications media (including radio and peer education) and reached nine in 10 adolescents, the Botswana program also reached a high proportion of the target audience. In South Africa and Guinea, however, the programs were less intensive and had a more limited reach. CONCLUSIONS: Interventions targeted at adolescents can be effective in changing attitudes and sexual behavior if they include multiple channels of communication, reach a substantial proportion of young adults and make contraceptives widely available. There remains on urgent need to identify ways to address young men sexual health concerns effectively.