The Guide to Community Preventive Service's methods for systematic reviews were used to evaluate the effectiveness of various approaches to increasing physical activity: informational, behavioral and social, and environmental and policy approaches. Changes in physical activity behavior and aerobic capacity were used to assess effectiveness. Two informational interventions ("point-of-decision" prompts to encourage stair use and community-wide campaigns) were effective, as were three behavioral and social interventions (school-based physical education, social support in community settings, and individually-adapted health behavior change) and one environmental and policy intervention (creation of or enhanced access to places for physical activity combined with informational outreach activities). Additional information about applicability, other effects, and barriers to implementation are provided for these interventions. Evidence is insufficient to assess a number of interventions: classroom- based health education focused on information provision, and family-based social support (because of inconsistent findings); mass media campaigns and college-based health education and physical education (because of an insufficient number of studies); and classroom-based health education focused on reducing television viewing and video game playing (because of insufficient evidence of an increase in physical activity). These recommendations should serve the needs of researchers, planners, and other public health decision makers.