<qa>  What is the risk of cardiovascular disease?As many as 60 of Americans do not engage in regular physical activity and 25 are completely inactive. The risk of cardiovascular disease is almost doubled among people who are physically inactive, comparable to the risks associated with increased systolic blood pressure, cigarette smoking, and elevated serum cholesterol. To make an impact on physical activity prevalence at the population level requires a research focus at the interface between clinical efficacy trials and large-scale dissemination studies. Studies at this interface must use proven interventions that are simultaneously effective and cost-efficient. Such interventions are the focus of this proposal. 