My study concerns the psycho-social determinants of health-related behaviors among adolescents. My research builds upon a body of literature that focuses on the mechanisms of adolescent health-endangering behaviors, and extends inquiries by examining cross-cultural influences on adolescents' health-related behaviors. I propose to conduct a comparative study of adolescents' health endangering behaviors between the U.S. and Japan. These countries will be compared because each of these cultural contexts has been considered to influence self-construction differently: self-enhancement in the U.S. and self-criticism in Japan. It is hypothesized that such differences in cultural contexts would change the patterns of relationships between psycho-social processes and health-endangering behaviors. I propose 24 months to complete the entire project, 12 months in the U.S. on fellowship and 12 months in Japan. Through this study, I hope to provide fundamental information to develop effective prevention programs for adolescents, which will ultimately address the need for such preventions for health care policy makers.