This study evaluated the overall efficacy and safety of two specific vasodilators--the alpha-blocker prazosin and the angiotensin-converting enzyme inhibitor captopril--in the treatment of mild-to-moderate essential hypertension. Because the current approach to antihypertensive treatment should consider possible drug-related changes in circulating lipid fractions, the present study investigated the effects of these two drugs on lipid parameters as well. Used either as single agents or in combination with hydrochlorothiazide, both drugs effectively reduced high blood pressure. Neither drug had adverse effects on the lipid profile in general, although there were significant differences between the effects of prazosin and captopril on total cholesterol, low-density lipoprotein cholesterol, and apolipoprotein B.