The informatin in this report summarizes the existing literature on the role of physical activity in preventing disease and on the status of interventions to increase physical activity, focusing on endurance-type physical activity. School-based interventions have been shown to be successful in increasing physical activity levels. With evidence that success in this arena is possible, every effort should be made to encourage schools to require daily physical education in each grade and to promote physical activities that can be enjoyed throughout life. A major conclusion of this report, though, is that daily enrollment in physical education classes has declined among high school students from 42 percent to 25 percent in 1995. Chapter 1 introduces and summarizes the report and presents the conclusions from each chapter. Chapter 2 offers a historical perspective, outlining the history of belief and knowledge about physical activity and health; then it reviews the evolution and content of physical activity recommendations. Chapter 3 describes the physiological responses to physical activity--both the immediate effects of a single episode of activity and long-term adaptations to a regular pattern of activity. Chapter 4 presents the evidence that physical activity reduces the risk of cardiovascular and other diseases. Data on patterns and trends of physical activity in the U.S. population are the focus of chapter 5. Lastly, chapter 6 examines efforts to increase physical activity and reviews ideas currently being proposed for policy and environmental initiatives. Each chapter contains references. (ND)