Forty six patients with stable effort angina were treated with a combination of propranolol, nifedipine, and isosorbide dinitrate which produced a more profound anti-antianginal effect than each of them given alone. The combination also exerted more marked antihypertensive and antiarrhythmic effects. The combined therapy with the three drugs caused a moderate reduction in heart rate and peripheral resistance, but failed to result in clear-cut disturbances in the orthostatic regulation of the circulatory system. There was a more infrequent and less pronounced ST-segment depression, less marked pressor responses and higher heart rate with the combined therapy during exercise; the cardiac index also increased as before therapy. Physical fitness increased to a greater extent than with monotherapy. The combined therapy with three drugs is indicated when monotherapy fails and that with two agents is indicated when patients have concurrent essential hypertension and cardiac arrhythmias.