To assess the effects of acebutolol and propranolol on resting left ventricular function, 21 patients with coronary artery disease were studied. A baseline echocardiogram was obtained on day 1, and in a double-blind, randomized, crossover study the patients received 40 mg propranolo every 8 hr for 1 wk, 300 mg acebutolol every 8 hr for 1 wk, and 1 capsule placebo every 8 hr for 1 wk. On days 8, 15, and 22, after an echocardiogram at 7:30 A.M. (i.e., 7.5 hr after the midnight dose), they received double-blind randomized, crossover medications (acebutolol 300 mg, propranolol 40 mg, or placebo). The echocardiogram was repeated at 1.2, and 4 hr after placebo or propranolol and at 2, 3, and 5 hr after acebutolol. The left ventricular end diastolic dimension, left ventricular end systolic dimension, percent systolic shortening of the left ventricular minor axis, and ejection fraction were determined. We found that there was no significant difference between control values for any of the above parameters and those obtained at 1, 2, 4, or 7.5 hr after propranolol or placebo and at 2, 3, 5, or 7.5 hr after acebutolol. We conclude that in the doses used, acebutolol and propranolol do not induce depression of resting left ventricular function in patients with coronary artery disease who have normal or near normal left ventricular function at rest.