A 9-week leisure education program to increase activity involvement and social interaction of institutionalized mentally retarded adults was investigated. A disproportional stratified (by residential unit) random sampling technique was employed to select 40 subjects from a total population of 243 mentally retarded persons. Subjects were randomly assigned to treatment and control groups. The hypotheses were that there would be no significant increase in activity involvement or social interaction of the subjects who participated in the treatment. Four ANCOVAs were conducted utilizing frequency and duration as the dependent variables for both social interaction and activity involvement. Length of institutionalization was the covariate. The grouping variables were treatment/control and level of retardation. The findings revealed the treatment had a significant effect only on frequency of activity involvement.