In a double blind cross-over study the effect of verapamil (Isoptin) 360 mg/d and propranolol 180 mg/d was evaluated in patients with stable angina of effort. The results of verapamil and propranolol treatment were compared to a single blind placebo period of 2 weeks. Both verapamil and propranolol caused a significant reduction in nitroglycerin consumption, days with angina pectoris and in severe angina attacks as compared to placebo. A 50% reduction in angina pectoris attacks and/or nitroglycerin consumption compared to placebo was demonstrated in thirteen of eighteen patients during verapamil treatment (P less than 0.01) and in seven of seventeen patients during propranolol treatment (P greater than 0.05). Of sixteen patients completing both treatment periods, ten were improved both on verapamil and propranolol, three on verapamil only, one on propranolol only, one was unchanged and one deteriorated on verapamil and propranolol. During exercise, maximum exercise capacity was increased during verapamil as compared to placebo (P less than 0.01) and propranolol (P less than 0.02). Maximum exercise capacity was not increased after propranolol as compared to placebo. These findings, that verapamil is at least as effective as propranolol in the treatment of angina of effort, are in accordance with other reported series.