An objective assessment of the efficacy of bevantolol was performed in 21 patients with chronic, stable angina using computer-assisted exercise testing and ambulatory ST-segment monitoring. Given once daily, 200 mg of bevantolol was compared with 200 mg of bevantolol given twice daily and with placebo, using a double-blind crossover technique. The mean exercise time with placebo was 7.4 +/- 0.6 minutes; this increased to 10.6 +/- 0.9 minutes (p less than 0.001) with once-daily bevantolol and to 9.4 +/- 0.9 minutes (p less than 0.001) with twice-daily bevantolol. The mean heart rate at rest was 80 +/- 3 beats/min with placebo; it decreased to 63 +/- 2 beats/min (p less than 0.001) with once-daily bevantolol and to 66 +/- 2 beats/min (p less than 0.001) with twice-daily bevantolol. The maximum exercise heart rate of 118 +/- 6 beats/min with placebo was reduced to 99 +/- 4 beats/min (p less than 0.001) on once-daily and 101 +/- 4 beats/min (p less than 0.001) on twice-daily bevantolol. There was a corresponding decrease in the rate-pressure product. The corrected maximum ST-segment depression was reduced from 0.3 +/- 0.06 mm min-1 with placebo to 0.2 +/- 0.03 mm min-1 (p less than 0.02) with once-daily and 0.2 +/- 0.04 mm min-1 (p less than 0.05) with twice-daily bevantolol. The mean hourly ambulatory heart rate was significantly reduced for 21 hours with once-daily and 22 hours with twice-daily bevantolol. The lowest mean minimum heart rate was 55 beats/min during twice-daily treatment. The mean number of episodes of ST depression over 24 hours in lead CM5 was decreased from 6.89 +/- 1.7 with placebo to 2.50 +/- 0.6 (p less than 0.001) with once-daily and to 3.72 +/- 1.3 (p less than 0.001) with twice-daily bevantolol. Three patients were withdrawn during the once-daily bevantolol regimen due to adverse experiences, and another patient was admitted for coronary artery bypass surgery after 25 days.(ABSTRACT TRUNCATED AT 250 WORDS)