Vagaries in the behavior of patients have long been recognized as important limiting factors in the satisfactory control of diabetes mellitus. Physicians are familiar with the fact that many adolescents omit use of their insulin, fail to sterilize their equipment, and "raid the icebox"—especially after conflicts with their parents. It is equally well known that many of the more obese patients of all ages are unable to curb their appetites and that this constitutes a major obstacle to the dietary control of a large part of the diabetic population. In addition, it has been often suspected, but not adequately demonstrated, that changes in the course of diabetes may result not only from the failure of the patient to follow the treatment regimen, but also from the direct metabolic effect of life stress. An increasing body of evidence now indicates that even when diabetic persons adhere strictly to their prescribed regimen,