Diuretics and adrenergic blocking agents have been used extensively in the treatment of hypertension. Recent studies have indicated that the thiazides and chlorthalidone have an adverse effect on lipid metabolism, by increasing plasma triglycerides, total cholesterol, and low density lipoprotein cholesterol in mildly hypertensive patients. These same agents produced little change in high density lipoprotein cholesterol. On the other hand, the loop diuretic furosemide adversely affected the cholesterol ratio by lowering high density lipoproteins (HDL) instead of increasing very low density lipoproteins (VLDL) or low density lipoproteins (LDL). The centrally acting drug methyldopa has also been reported to lower HDL, while another centrally acting drug, reserpine, appears to be lipid-neutral. Practically all the beta blocking agents increase triglycerides or decrease HDL, thus yielding an adverse cholesterol ratio. The alpha 1-adrenergic blocking agent prazosin has been shown in several studies to have no adverse effect on the lipid profile.