In a randomized, double-blind study oral doses of 50 mg carvedilol (Dilatrend) were compared with 40 mg propranolol in 16 male patients with coronary heart disease, CHD [12 without significant stenoses following percutaneous transluminal coronary angioplasty (PTCA), 4 with multivessel disease]. Bicycle ergometry in the supine position was performed before and 80 min after drug application; measurements were done at rest, during and after exercise. Clinically, the total exercise time and the onset of angina and exhaustion were noted, while the investigated hemodynamic parameters were heart rate, systemic and pulmonary pressures and resistances, cardiac index, and lower limb blood flow. Clinically, carvedilol improved the exercise tolerance more than propranolol as regards angina and exhaustion. Hemodynamically, carvedilol did not lead, as the classic betablocker propranolol does, to an increase in systemic or pulmonary resistance, to a decrease in cardiac output, or to an increase of the pulmonary capillary wedge pressure during exercise, but instead caused opposite changes. In contrast to propranolol, the post exercise lower limb blood flow had increased significantly. The differences in action between the two betablockers can be explained by the vasodilating properties of carvedilol. Due to these acute effects, carvedilol may be preferred to propranolol in the treatment of CHD patients with hypertension, peripheral occlusive artery disease, and/or coronary vasospasm.