Research examining the effects of sports participation on children and youth is reviewed from the perspective of psychological and physical development. Statistical information regarding the participation rate in different kinds of youth sports is given. The effects of prolonged athletic activity on bone, muscle, and adipose tissue growth is considered, as well as the general effect of sports on overall growth. Injuries due to repeated stress and physical (muscular) trauma, and biological maturation are also considered. The psychological effects are examined through a discussion of the meaning of competition and of the socializing effects sports organizations exert on participants. The monograph terminates with a discussion of unresolved problems in youth sports competition, including the exclusion and retention of athletes, possible alternatives to highly competitive athletic programs, and the need for qualified and sensitive adult leaders in the field of youth sports. (LH)