This article presents an overview of major developments in physical activity and exercise for health promotion and disease prevention during the past 10 years. The importance of physical activity to physical and mental health was increasingly recognized. Assessment methods appropriate for diverse population groups were developed, and understanding of correlates of regular physical activity improved. Many studies focused on moderate activity that can be integrated into people's everyday lives. Research in community, school, and health care settings demonstrated that interventions based on cognitive-behavioral theories can change physical activity. Nevertheless, physical activity remained at low levels in most population subgroups throughout the past decade. Psychologists can make important contributions to efforts to address this ongoing challenge to public health.