Rest and exercise systemic hemodynamic parameters, coronary blood flow, and myocardial energetics were assessed before and 15 min after the sublingual administration of 20 mg of nifedipine in 10 patients with idiopathic congestive cardiomyopathy. When compared with control, nifedipine increased rest and exercise cardiac index by 37% and 28%, respectively (p less than .001). Peripheral vasodilation was demonstrated with a drop in systemic arterial pressure, exercise pulmonary capillary wedge pressure, and systemic vascular resistance (p less than .05). The calcium-channel blocker did not alter myocardial oxygen consumption; however, coronary blood flow increased by 32% at rest (p less than .01) while coronary vascular resistance diminished both at rest and after exercise compared with control (p less than .05). Nifedipine elicited a decrease in the rest and exercise aortocoronary sinus oxygen difference while the coronary sinus oxygen saturation increased (p less than .01). In this group of patients with idiopathic congestive cardiomyopathy, nifedipine enhanced myocardial performance while increasing coronary blood flow and favorably altering the myocardial oxygen supply-demand balance.