32 patients with stable angina and a positive symptom-limited exercise test (SLET) were investigated in a double-blind randomized trial in order to assess the therapeutic efficacy of bopindolol or atenolol on the incidence of angina pectoris and on angina pectoris threshold heart rate (ATHR). After a washout and placebo period of 2 weeks, each of two drugs were applied in dosages of 0.5 mg bopindolol and 50 mg atenolol. The dosage was increased every month up to 2 mg bopindolol and 200 mg atenolol. At the end of every period, the patients were retested by SLET. After 3 months of active treatment, we noticed that the incidence of angina attacks was lower in the bopindolol group (2.,45 vs. 3.29). The resting heart rate was also lower in the bopindolol group (55.89 vs. 63.38). No statistical significance was found between the peak work rate, ATHR, exercise duration and S-T depression. The rate-pressure product was lower in the bopindolol group. We concluded from this that bopindolol and atenolol are active in decreasing the incidence of angina, the former being more effective. Exercise performance and cardiocirculatory parameters did not differ between the two groups.