To investigate the actions of nitroglycerin on left ventricular (LV) systolic and diastolic functions in coronary artery disease, high-fidelity LV pressures and LV biplane cineventriculograms were simultaneously made for 16 patients with old myocardial infarction before and 5-10 minutes after the sublingual administration of 0.6 mg of nitroglycerin. Before and after the nitroglycerin administration, heart rates were maintained constant at an average of 73 beats/min by right atrial pacing. LV volume and segmental wall shortening were derived from frame by frame (20 msec) analysis of LV biplane angiograms. The results were as follows: There were significant decreases in LV end-diastolic pressures (-44%) and volumes (-10%), mean arterial pressures (-12%) and LV systolic pressures (-16%), suggesting preload and afterload reductions. Global ejection fraction was significantly increased from 0.41 to 0.45, while cardiac output decreased significantly (-8%) because of a decrease in preload. Augmented ejection fraction was associated with increased shortening of the normal and hypokinetic segments. The dyskinetic segment remained unchanged. Thus, the degree of nitroglycerin-induced potentiation of LV regional contraction seemed related to the degree of regional myocardial ischemia and fibrosis. The time constant (T) of the LV pressure decay was slightly but significantly decreased, which may imply the possibility of improving LV relaxation using nitroglycerin. LV early filling significantly decreased as evidence by a fall in the peak filling rate (PFR) and the normalized PFR. The decrease of the PFR, however, may be related mainly to preload reduction by nitroglycerin. In 11 of 16 patients, there was a displacement of LV diastolic pressure-volume curves downward and to the left. The shift of the curves may be caused by the effects of ventricular interaction and/or the pericardium.