The metabolic effects of acebutolol, a cardioselective beta-adrenergic blocker, and of propranolol, a nonselective beta blocker, were evaluated. Our subjects were 20 men with chronic stable angina; none had diabetes. An initial 4-wk, single-blind control phase was followed by two drug treatment periods, each a 3-wk double-blind titration phase (using increasing doses of acebutolol or propranolol), followed by a 5-wk double-blind maintenance phase. Metabolic studies were performed at the end of the control and maintenance phases. Propranolol induced elevation in basal serum glucose concentrations and both propranolol and acebutolol decreased glucose tolerance at 2.5 and 3 hr. There was no noticeable effect on insulin secretion by either drug. Neither propranolol nor acebutolol induced hyperlipidemia. There was a small decrease in total serum cholesterol after propranolol. Both drugs decreased low-density lipoprotein cholesterol. No effects were noted on the levels of serum triglycerides, high-density lipoprotein cholesterol, or free fatty acids.