Carvedilol 25 mg b.d. was compared with nifedipine s.r. 20 mg b.d. for subchronic treatment of patients with chronic stable angina. After washout and placebo run-in, 163 patients were randomly and double-blindly allocated to one of the two treatment groups. Two symptom-limited seated bicycle exercise tests were performed on placebo in order to confirm stable baseline conditions. After 4 weeks of active treatment, a further exercise test was performed in the morning, 12 h after the preceding dose. Diary cards were kept by the patients throughout the trial in order to record angina attacks and glyceryl trinitrate consumption. Carvedilol seemed to be somewhat more effective than nifedipine s.r. for improving exercise tolerance and exercise time to onset of angina and 1 mm ST-segment depression. Although there were highly statistically significant differences vs placebo, the two treatment groups did not differ significantly. No difference between treatment with carvedilol and nifedipine s.r. was found regarding angina symptoms and glyceryl trinitrate consumption during daily life. Adverse events were less frequently reported in the carvedilol group than in the nifedipine group. Generally, however, both agents were well tolerated. Carvedilol therapy for chronic stable angina seems to be both efficacious and safe.