The social worlds of the adolescent and their potential effect on health behavior are the focus of this chapter. Social cognitive theory, resiliency theories, and the theoretical implications of focusing on lifestyle patterns of adolescents are discussed in order to provide a theoretical frame of reference for viewing the complex interactions between individual factors, socioenvironmental factors, and health-related behaviors among adolescents. Factors within the different social environments (family, school, peers, and community) are discussed and some general recommendations based upon empirical research findings and theories about adolescent health behavior are made.