This paper reviews several psychosocial theories that have been applied to the study of adolescent health behavior. Some of these theories have existed for several decades and, though not originally intended for this purpose, have proven quite useful in predicting and explaining many different types of health-relevant behaviors. During the last 10–15 years, however, there has been a significant increase in the application of social psychological theories to the examination of what is increasingly being seen as a social-psychological phenomenon: health risk behavior among adolescents. This interest has been prompted, in part, by an appreciation of the value of dual-processing principles in explaining these behaviors, and, in particular, a recognition that much adolescent health risk behavior: a) is not always planful or premeditated, and b) involves both heuristic and analytic processing. The paper includes discussion of how dual-processing principles and social-psychological theories can inform intervention efforts.