In diabetic patients, it has been suggested that angiotensin converting enzyme inhibitors may be associated with unexplained hypoglycaemic episodes. Such a side effect may limit the use of these drugs in diabetic hypertensive patients. Ten insulin-dependent diabetic patients mean age 38.4 +/- 13.1 years, mean diabetes duration 10.3 +/- 6.6 years (m +/- SD) were selected on the basis of good glycaemic control: HbA1: 7.6 +/- 0.9 per cent (upper limit of normal value less than 7.5 per cent) on continuous subcutaneous insulin infusion. In a double blind study, they were randomly and successively allocated for a 3 months period to enalapril 20 mg daily or placebo. Before treatment, after enalapril and placebo, mean blood glucose values, HbA1, daily insulin dosage were recorded as well as the number of clinical and biological (less than 3 mmol/l) hypoglycaemic episodes. Peripheral insulin sensitivity was assessed by euglycaemic insulin clamp technique. Compared to placebo, enalapril did not induce any modification of daily insulin dosage, glycaemic control. The incidence of hypoglycaemic episodes was similar. Neither peripheral insulin sensitivity was modified by enalapril. In the conditions of this study, enalapril did not interfere with glycaemic control in insulin-dependent diabetics in good metabolic control.