The long-term antianginal effect of orally administered verapamil over 1 year of continuous treatment was assessed in 11 patients with effort-induced angina. In the short-term phase of the study, patients were given, in random order, placebo and verapamil (360 mg/day). The tolerated work load during a bicycle exercise test was 531.8 +/- 123.0 kg/min on placebo and 763.6 +/- 124.7 kg/min on verapamil (p less than 0.001). Subsequently all patients entered a long-term study of 1-year continuous treatment with 120 mg t.i.d. verapamil. The tolerated work load at 8-week (736.4 +/- 105.1 kg/min) and 1-year (804.6 +/- 101.1 kg/min) tests did not significantly differ from the results in the short-term study. The average verapamil plasma level was 138.5 +/- 90.6 ng/ml before and 357.8 +/- 199.2 ng/ml 90 min after drug administration; the average norverapamil plasma levels were, respectively, 248.0 +/- 84.4 and 368.0 +/- 135.9 ng/ml. There was no correlation between verapamil or norverapamil plasma concentrations and the antianginal effect. No patient developed signs of heart failure during the treatment. Two patients had mild constipation. The average P-R interval was slightly, although significantly (p less than 0.01) prolonged, but no patient developed first-degree atrioventricular block. We conclude that verapamil proves an effective and safe drug in the treatment of effort-induced angina; the beneficial effects of the short-term treatment are sustained during 1 year of continuous treatment.