This booklet summarizes results of research and literature reviews that had been collected in a source book titled "Physical Activity & Well-Being" and published in 1986 by the National Association for Sport and Physical Education. The evidence presented suggests that exercise can reduce or delay the undesirable effects of many degenerative diseases and concurrently serves as a therapeutic agent in mental and physical illnesses. Separate sections of this booklet describe: (1) the benefits of physical activity; (2) motor skill acquisition; (3) physical growth and biological maturation; (4) skilled performance and health-related fitness; (5) neuromuscular function and academic achievement; (6) mental, social, and moral development; and (7) special conditions, aging, and activity. A position paper is also presented dealing with the contributions of physical activities to well-being. A glossary of terms is included. (CB)