Terazosin is a selective alpha 1-adrenoceptor antagonist; its actions on the serum lipoprotein profile were compared with those of the cardioselective beta-adrenoceptor antagonist atenolol in 40 patients with mild to moderate hypertension. Atenolol and terazosin were titrated over six weeks until blood pressure control (diastolic blood pressure less than 90 mmHg or greater than 10 mmHg fall in blood pressure) or a maximum dose of atenolol 100 mg or terazosin 10 mg had been achieved. Patients not controlled were then prescribed additional diuretic therapy (cyclopenthiazide 0.5 mg and potassium 1200 mg). At each visit blood pressure and adverse events were recorded; plasma lipids were measured at baseline, six and 12 weeks. During titration there was a linear decrease in systolic (-29 mmHg on atenolol and -24 mmHg on terazosin) and diastolic blood pressure (-17 and -12 mmHg) in both groups without subsequent change over the next six weeks; atenolol reduced heart rate (-11 bpm) without change on terazosin. During the initial six weeks the total cholesterol fell in both groups; however, there were significant between-treatment differences in triglyceride responses with a fall on terazosin and a rise on atenolol. Comparing atenolol and terazosin over the total 12 week study (irrespective of thiazide treatment) increased triglyceride levels and reduced cholesterol ratios and HDL were demonstrated on atenolol, contrasting with reduced triglyceride levels and elevated HDL and cholesterol ratios of terazosin.(ABSTRACT TRUNCATED AT 250 WORDS)