Background: Using data from a statewide relationship education (RE) program targeting a diverse adolescent sample, this study examined RE implementation in classroom environments. Objective: The purpose of this study was to explore (1) whether there is a beneficial RE program effect for change in individual attitudes toward sexual delay, (2) whether individual factors--student gender and sexual activity--predict change in attitudes toward sexual delay for students experiencing the intervention, and (3) whether classmate characteristics influence individual change in attitudes toward sexual delay. Methods: This study utilized multilevel modeling procedures to examine both individual- and classroom-level predictors of change in attitudes toward sexual delay. Results: At the individual level, results indicated that females demonstrated more change in attitudes toward sexual delay than males and students who were sexually active demonstrated less change toward sexual delay compared with students who were not sexually active. At the classroom level, both racial composition and the proportion of sexually active classmates influenced individual attitude change. Although students in classrooms with higher proportions of African American peers demonstrated less attitude change toward sexual delay, the proportion of sexually active peers in the classroom appeared to be a more salient aspect of classmate composition. Conclusions: Overall, this study supports the importance of considering both individual characteristics as well as social context when assessing program experience and effectiveness. Implications for future research and practice are offered.