The effect of treatment with enhanced external counterpulsation (EECP) on exercise hemodynamics and myocardial stress perfusion in 27 patients with chronic stable angina was studied. A majority (22/27 or 81%) of patients improved their exercise tolerance after EECP treatment, and a similar percentage (21/27 or 78%) of patients improved their radionuclide stress perfusion images. Post-EECP maximal exercise heart rate and blood pressure, while demonstrating a linear relation with exercise duration, did not increase significantly despite the increased exercise duration. This suggests that the increase in exercise duration after treatment with EECP is due to both improved myocardial perfusion and altered exercise hemodynamics. EECP therapy thus appears to exert a "training' effect, decreasing peripheral vascular resistance and the heart rate response to exercise. Coronary disease patients may improve their exercise tolerance after EECP because of both improved myocardial perfusion and a decrease in cardiac work load.