Captopril (37.5 mg daily) was administered to 64 hypertensive patients for 16 weeks. During treatment, systolic and diastolic blood pressures decreased significantly (from means of 164/98 mmHg before treatment to 150/90 mmHg at four weeks and 142/86 mmHg at eight weeks; P less than 0.001), but serum levels of total cholesterol, triglycerides, lipoprotein cholesterol, lipoprotein triglyceride, and apolipoproteins showed no significant changes. Scores on the atherogenic index did not change. Patients with high initial total cholesterol levels and low high-density lipoprotein cholesterol levels tended to improve their lipid levels. It is concluded that captopril does not adversely affect serum lipoprotein metabolism.