Acebutolol, a beta-1 selective beta blocker with intrinsic sympathomimetic activity has been shown to be an effective agent in chronic angina pectoris therapy, with twice or three times daily dosing. The long-term effects of 400 mg of acebutolol given only once a day versus placebo on exercise hemodynamics, ST segment depression, and rate pressure product were studied. Eleven patients (mean age, 60 +/- 12 years) with hypertension and chronic angina pectoris were enrolled. Resting heart rate was not significantly altered after therapy, (80 vs 72 bpm). Objective measurements from exercise treadmill tests showed significant reduction in peak heart rate from 130 to 103 bpm, systolic blood pressure from 197 to 167 mm Hg, rate pressure product (from 25 to 18 bpm-mm Hg X 1000), and ST depression in patients receiving acebutolol compared with those receiving placebo. No significant adverse effects were reported. These data indicate that acebutolol may be efficacious as once daily therapy for chronic stable angina pectoris.