This chapter presents a model for conceptualizing adolescent beliefs about alcohol and other drug use and identifies potential prevention strategies aimed at modifying these beliefs. A central thesis is that adolescents’ beliefs about themselves and their peers, parents, and communities are important predictors of their behavior. Consequently, the chapter is organized around adolescents’ beliefs about intrapersonal, interpersonal, and extrapersonal influences on alcohol and drug use. I begin by documenting the extent of the problem of alcohol and drug use among young adolescents and then focus on literature related to beliefs, attitudes, and perceptions. Finally, I review interventions related to beliefs that may be effective in reducing substance use. The term beliefs refers to attitudes, perceptions, and expectations.