Behavioral science provides the foundation for physical activity interventions. The mediating variable framework is used to assess the status of physical activity interventions and the roles that are, or could be played, by behavioral theory. Twenty-five physical activity intervention studies and 45 physical activity correlational studies were found in the literature, tabulated, and included in the analysis. Behavioral interventions for promoting physical activity have worked primarily when participants were motivated enough to volunteer or when a school-based physical education program changed. In most cases, behavioral or psychosocial theory accounted for 30% or less of the variability in physical activity behaviors. Most intervention studies do not measure mediating variables, and when they do, they do not systematically effect changes in all the mediating variables on which they are predicated. To increase the effectiveness of physical activity interventions, more physical activity research should focus on a better understanding of the predictors of physical activity and toward interventions demonstrated to effect change in these predictors of physical activity. Changing the focus to basic behavioral and social science and mediator change research should provide a more systematic and cost-effective approach to increasing the effectiveness of physical activity interventions.