62 male diabetics worked in hospital workshops while their metabolic state was assessed. In each patient work activity, periods of work and rest and employment-related eating breaks were maintained. The metabolic state was regularly tested during physical activity simulating their actual employed work. In these circumstances there was a definite fall in blood sugar levels in the course of the day. Low values and hypoglycaemia were more frequent depending on the degree of physical activity, especially in the morning. The management of diabetes was adjusted to these metabolic requirements. Insulin dose was decreased and (or) carbohydrates were taken more frequently or in larger amounts. This adjustment in diabetes management was recommended to the diabetics for their normal everyday employment activity. Control of the diabetes was better on discharge from hospital and for some time afterwards.