Summary. Two groups of insulin-treated outpatients (one followed up at the Hotel-Dieu Hospital and the second mainly supervised by general practitioners) were chosen at random in 1978. The two populations were comparable in age, age at diagnosis, sex, level of education, overall activity and socio-professional and economic status. Outpatients followed up in the diabetic unit had better blood glucose control, with about the same number of hypoglycaemic reactions as patients followed up in general practice. This better control was associated with more social activity and less visits to the physician, despite the fact that patients attending the hospital spent more money on their diet and had more daily insulin injections. All these differences remain significant after adjustment for the duration of diabetes. It may be inferred that attempts to improve control in insulin-treated patients are associated with a more active life and with no increase in the frequency of hypoglycaemic reactions.