A population-wide, community-based program in cardiovascular disease prevention, the Minnesota Heart Health Program (MHHP), has been designed to promote more frequent and vigorous physical activity in North American communities, along with improved eating and smoking patterns. The physical activity component of this broad-based education strategy is based on the facilitation which physical activity provides to lowering of other risk characteristics for heart disease and its enhancement of other healthy behaviors and on the potential for prevention of elevated risk in the first place. The rationale for a population strategy to complement medical approaches to prevention is that exercise patterns are largely socially learned and culturally determined. The MHHP Physical Activity Program is implemented through three major education strategies: direct education, community organization, and mass communications. Early results from this 10-year project indicate that it is feasible to enter U.S. communities and to involve their leadership actively in MHHP activities of health promotion. Moreover, attitudes, knowledge, awareness, participation, and behaviors related to exercise and eating patterns appear to be changed by the program. Nevertheless, there are problems in the design, implementation, analysis and interpretation of population changes in physical activity and other health behaviors in community demonstration programs. These issues, along with their solutions, should provide useful information for medical science and for the public health about population strategies of disease prevention and health promotion.