Hypertension, common in diabetic patients, worsens not only the risk of cardiovascular complications, but also that of microangiopathic complications (nephropathy, retinopathy) of diabetes mellitus. It is thus important to ensure the perfect control of even mild hypertension in diabetic patients. However, treatment sometimes becomes difficult given that certain categories of antihypertensive drugs interfere with blood glucose control and/or lipid metabolism, interfere with the symptomatology of hypoglycemia, or promote orthostatic hypotension, a complication of autonomic neuropathy. A study was undertaken to determine the effects of rilmenidine, administered for 16 weeks, in 29 diabetic patients treated with insulin and experiencing mild-to-moderate hypertension (supine diastolic blood pressure, 96.7 +/- 0.5 mmHg). Administered as single-drug therapy, rilmenidine rapidly normalized blood pressure (systolic blood pressure, less than 160 mmHg; diastolic blood pressure, no more than 90 mmHg--supine) in 17 patients; this persisted throughout the trial period. Addition of a diuretic after 12 weeks in the remaining 12 patients led to normalization of blood pressure in nine additional patients. Blood glucose control (evaluated at home by weekly blood glucose measurements and by glycosylated hemoglobin levels) was unaffected by treatment. Plasma levels of cholesterol (total, high-density lipoprotein and low-density lipoprotein), triglycerides and proteinuria (or microalbuminuria) showed no change during the course of the trial. In conclusion, rilmenidine offers an effective and safe treatment for mild-to-moderate hypertension in diabetic patients treated with insulin and does not interfere with their blood glucose control.