The investigation examined the role of physical activity programs in the modification of the motor, intellectual, social, and emotional development of educable mentally retarded children and minimally brain injured children. Forty nine classes of children (275 educable mentally retarded and 206 minimally brain injured) participated in 20 weeks of instructional programs. Classes were randomly assigned to one of four treatments: two were physical education programs (one individually oriented, the other group oriented); one was an art program (Hawthorne effect); the fourth, a control (usual program). A battery of 32 tests was administered prior to and at the end of the experiment. Children in the special experimental programs elicited greater positive changes in their motor, intellectual, and emotional behavior than those in the control program. Of the special programs, the physical education programs were superior in modifying motor performance, the art program in altering emotional behavior, and neither was superior in modifying intellectual behavior. The individually oriented physical education program elicited greater gains than the group oriented program in measures of motor, intellectual, and emotional behavior. Positive behavior changes occurred more frequently in the older than younger, more often in the brain injured than the retarded, and more frequently in the boys than the girls. (Author)