We studied 44 patients (group I: 9 with insignificant disease and group II: 35 with significant coronary artery disease) by nuclear angiography during the controlled increase in heart rate by atrial pacing to evaluate the effect of 20 mg of sublingual nifedipine on left ventricular function. Left ventricular volumes were calculated using count-derived changes: end-diastolic (EDE), end-systolic (ESE), stroke volume (SVE) and cardiac output equivalents (COE) and ejection fraction (EF) and ejection rate (ER) were calculated during basal sinus rhythm (C) and at the maximal atrial pacing (AP) rate with and without nifedipine. In normal subjects, AP decreased ventricular volumes. The administration of nifedipine decreased blood pressure but had no further effect on left ventricular volume. In the ischemic ventricle, AP produced reversible ventricular wall paresis with a smaller decrease in EDE, an increase in ESE and a significant fall in EF. Nifedipine induced a striking improvement in EF and ER. This was probably a consequence of afterload reduction and increased coronary blood flow.