Amlodipine, a dihydropyridine calcium antagonist, was compared with placebo in a double-blind cross-over study in 16 patients with angina. After a 2-week single-blind placebo period, patients entered a double-blind crossover phase alternating between 4 weeks of placebo and 4 weeks of amlodipine, 10 mg once daily. The two 4-week periods were separated by a 1-week single-blind placebo washout period. The efficacy of drug therapy was measured using frequency of angina, nitroglycerin consumption, peak oxygen consumption during a maximal treadmill exercise test, and endurance time during a separate submaximal exercise test performed at 70% of the peak work capacity that had been determined before randomization. Compared with single-blind placebo there was a reduction in angina frequency during double-blind placebo and amlodipine, whereas nitroglycerin consumption was significantly reduced only by amlodipine. Amlodipine produced a significant increase in peak oxygen consumption and endurance time during the submaximal exercise test when compared with single-blind and double-blind placebo periods. Patients tolerated both placebo and amlodipine without clinically significant side effects.