Objective: This paper describes the development and proposed behavioral theory underlying Shattered Dreams, a school-based intervention aimed at reducing underage drinking and alcohol-related crashes. The program has been widely disseminated; however, few published studies have conceptualized the underlying behavioral change mechanisms. Methods: We applied constructs from the transtheoretical model and social cognitive theory in order to operationalize change among program participants. Results: Program components align well with constructs of the trans-theoretical model and social cognitive theory. Conclusions: Mapping program components on to well-established theories may prove useful in quantifying the program's impact on underage drinking and driving outcomes. [ABSTRACT FROM AUTHOR]