The effects of oral propranolol and digoxin and digoxin alone and in combination on angina frequency, heart size, systolic time intervals and treadmill exercise tolerance, were assessed in 20 patients with coronary heart disease. Oral propranolol alone reduced the average frequency of angina pectoris from 16 to 7 attacks per week (P less than 0.02). However, the mean duration of exercise was not significantly improved because 8 patients with abnormal left ventricular function exhibited a decrease in exercise tolerance. Combined propranolol and digoxin improved exercise tolerance in these patients, and, consequently, mean exercise duration in all patients increased significantly from the control value of 390 +/- 42 to 458 +/- 46 s (P less than 0.01). Propranolol alone also resulted in a significant increase in left heart size from 46.5 +/- 1.3 to 47.7 +/- 1.5 mm/m2 (P less than 0.001), which was reversed by the addition of digoxin. Therefore, oral propranolol combined with digoxin is advantageous in patients with angina pectoris who have abnormal ventricular function or large hearts.