The effectiveness of chronic treatment with nifedipine in patients (pts) with a history of stable angina on effort has been evaluated in a double-blind study in 15 subjects of both sexes, aged 45 to 65 years. All pts underwent diagnostic cardiac catheterization and selective coronary angiography, which showed stenosis of one or two main coronary vessels between 50 and 70%. The pts, after 2 weeks of observation, underwent erect bicycle exercise test with increasing workloads. After 4 weeks of treatment with nifedipine or placebo the stress test was repeated. Nifedipine treatment reduced the weekly number of anginal attacks as well as the weekly number of nitroglycerin tablets consumed by the pts, increased maximum workload tolerated and reduced the S-T segment depression for the same workload, meanwhile heart rate and blood pressure did not change significantly either at rest or during exercise. The result of this study indicate that nifedipine is useful in the treatment of pts with stable angina on effort.