This single masked, crossover trial will randomize children with Sensory Modulation Dysfunction (SMD) to either Occupational Therapy (OT), alternative treatment (Activity Protocol), or delayed treatment (initially the control group). Children are assigned to one of the three treatment groups using a random numbers table with block randomization. Assignments are made by the research assistant, who is masked to assessments, parent priorities, and family needs/characteristics. Using block procedures, the first child is randomly assigned to treatment group A, B, or C. The next child entered to the study at that age, gender and socioeconomic status (parents' education) is randomly assigned to one of the two remaining groups. The third child meeting age, gender and SES criteria is automatically assigned to the remaining group. This procedure reduces seasonal confounds and chance variation between group characteristics. The order of treatment by group is: GROUP A (OT - 1st 10 weeks; Activity - 2nd 10 weeks); GROUP B (Activity - 1st 10 weeks; OT - 2nd 10 wks); GROUP C (Wait list - 1st 10 weeks; OT - 2nd 10 wks; Activity - 3rd 10 wks). Inclusion in the study is based on standardized assessments of physiological reactivity after a "Sensory Challenge Protocol", a technique developed by this research group and published in several medical journals. Standardized measurements of physiologic, behavioral and emotional status, are administered before treatment, after each treatment condition, and after all treatments are completed by investigators masked to treatment; and including the following: