Two hundred newly diagnosed, fat diabetics were studied to determine whether control of the diabetes depended on loss of weight or on carbohydrate restriction alone. Satisfactory control was achieved by dietary treatment alone in 159 patients 30 required oral hypoglycaemic drugs and 11 were 18 of whom had actually gained weight. Of the remaining patients, 30 required oral hypoglycaemic drugs and 11 were still uncontrolled but not yet on other treatment.The mean initial excess weight of all 200 patients was 28%. Of those who remained uncontrolled on diet alone the mean initial excess weight (31%) was slightly but not significantly greater than that of those who were controlled (27%). Patients who were controlled lost slightly more weight than patients who were not, but their excess weight at the time of control was still 21%.We conclude that in 80% of obese diabetics control can be achieved by diet alone and that it is usually independent of weight loss.