Social support plays a positive role in compliance and other health behaviors. The purpose of this study was to investigate the role of social support in compliance and other health behaviors for patients with sickle cell disease and diabetes. Subjects consisted of 49 patients with sickle cell disease and 78 patients with diabetes attending outpatient clinics at an urban hospital. Subjects were given questionnaires which assessed their appointment-keeping behavior, adherence to health activities, and social support. The results indicated that social support was significantly associated with appointment-keeping behavior and adherence to health activities in both the sickle cell and the diabetic sample. Implications of the study findings for improving compliance by increasing social support are discussed.