This study assessed the effects of a course of enhanced external counterpulsation (EECP) therapy on systolic and diastolic cardiac function using echocardiography to measure left ventricular ejection fraction (LVEF), end-systolic volume (ESV), end-diastolic volume (EDV), systolic wave (Sm), early diastolic wave (Ea), Vp, E/Ea, E/Vp, and diastolic function grade in 25 patients before and after 35 hours of EECP. EECP reduced ESV and EDV and increased ejection fraction significantly in patients with baseline LVEF < or = 50% (P=.018, .013, .002), baseline E/Ea > or = 14 (P=.032, .038, .007), baseline grade II or III diastolic dysfunction (decreased compliance) (P=.014, .032, .027), baseline Ea <7 cm/s (P=.015, .024, .001), and baseline Sm <7 cm/s (P=.017, .016, .006), but not in patients with baseline LVEF >50%, baseline E/Ea <14, baseline normal diastolic function or grade I diastolic dysfunction (impaired relaxation), baseline Ea > or = 7 cm/s, and Sm > or = 7 cm/s. These results demonstrate improved systolic and diastolic function in selected patients and provide new insight into potential clinical applications of EECP.