The subjects were 15 patients, aged 53 to 74 years, with noninsulin-dependent diabetes mellitus and mild to moderate hypertension. Each received 20 to 40 mg of nitrendipine daily for six months. Mean supine blood pressures decreased significantly from 177/102 mmHg before treatment to 164/95 mmHg at three months and continued to decline during the following three months. Diastolic blood pressure was reduced to less than 90 mmHg in eight of the 15 patients. No changes in heart rate, glycemic control (serum levels of glucose, C-peptide, glycosylated hemoglobin, and fructosamine), or serum lipid levels (cholesterol and its lipoprotein fractions, triglycerides, and apolipoproteins A1 and B) were noted. It is concluded that nitrendipine is safe and effective in the treatment of hypertension in diabetic patients.