This study compared the effects of occupational therapy, using a sensory integration (SI) approach and a control intervention of tabletop activities, on the frequency of self-stimulating behaviors in seven children 8–19 years of age with pervasive developmental delay and mental retardation. Daily 15-min videotape segments of the subjects were recorded before, immediately after, and 1 hour after either SI or control interventions performed during alternating weeks for 4 weeks. Each 15-min video segment was evaluated by investigators to determine the frequency of self-stimulating behaviors. The results indicate that self-stimulating behaviors were significantly reduced by 11% one hour after SI intervention in comparison with the tabletop activity intervention (p = 0.02). There was no change immediately following SI or tabletop interventions. Daily ratings of self-stimulating behavior frequency by classroom teachers using a 5-point scale correlated significantly with the frequency counts taken by the investigators (r = 0.32, p < 0.001). These results suggest that the sensory integration approach is effective in reducing self-stimulating behaviors, which interfere with the ability to participate in more functional activities.