The antiangina effects of atenolol, 50 to 200 mg once daily, or nifedipine, 10 to 30 mg 3 times daily, were evaluated in a multicenter, randomized, double-blind, parallel study of 39 patients with known symptomatic coronary artery disease. Treatment was titrated to produce at least a 30% increase in treadmill exercise duration over placebo baseline and then maintained at that dosage for an additional 3 weeks. Both treatments produced significant (p less than 0.001) increases in duration of exercise, total work and exercise capacity when compared with placebo baseline. These improvements in exercise performance were obtained with significant (p less than 0.001) reductions in both ST-segment depression and rate-pressure product for atenolol compared with nifedipine. Furthermore, the total angina attack rate and rate at rest were significantly (p less than 0.01) less frequent with atenolol than with nifedipine. Hence, the antiischemic effects of atenolol exceeded those of nifedipine, based on ST-segment depression and rate-pressure product at comparable workloads.