The antianginal activities of nicorandil, 10 and 20 mg bid, and metoprolol, 100 mg bid, were compared in patients with stable effort angina pectoris in a randomized, double-blind parallel group study lasting 7 weeks. Twenty patients were enrolled into the trial and 16 patients completed the study. To evaluate the anti-ischemic effects of the two drugs, a treadmill exercise test was performed after a 1-week placebo run-in period and 6 weeks of treatment. On the same occasions, weekly sublingual nitroglycerin consumption and the number of anginal attacks were also recorded in the patient's diary. The total duration of exercise increased significantly with both nicorandil, 10 and 20 mg, and metoprolol (p < 0.01). Similar improvements were observed in the time to onset of ischemia with both treatments (p < 0.01). The double product at maximal comparable workload (MAX 1) was reduced with the two drugs (p < 0.05 for nicorandil and p < 0.01 for metoprolol), while at the maximal exercise time (MAX 2) it was reduced with metoprolol (p < 0.01) and slightly but not significantly increased with both doses of nicorandil. Weekly sublingual nitroglycerin consumption and anginal attacks were also significantly reduced a similar manner by both treatments (p < 0.01). In conclusion, nicorandil, 10 and 20 mg bid, exerted an anti-ischemic effect comparable with that of metoprolol in patients with stable effort angina pectoris.