Left ventricular systolic function and compliance were assessed in 15 cases of pulmonary atresia with intact ventricular septum. The left ventricular ejection fraction measured from cineangiography was used for the evaluation of the systolic function. The end-diastolic pressure (EDP), left ventricular compliance index at end-diastole (dv/dp), and left ventricular stiffness constant K were used as compliance indices. The mean left ventricular ejection fraction was slightly diminished. The right ventricular end diastolic pressures (RVEDPs) correlated significantly (r = 0.90) with the left ventricular end diastolic pressure (LVEDP). On the basis of left ventricular compliance, two distinctive groups of patients could be identified: Group I consisted of Patients 1 to 7, all with impaired left ventricular compliance. A shunt operation was the basic palliation in this group. None of these patients survived infancy. Group II consisted of Patients 8 to 15, all with normal left ventricular compliance. Pulmonary valvotomy as well as aortopulmonary shunts were the basic palliative procedures in this group. Six of eight patients in this group are long-term survivors. No difference was found in right ventricular size, tricuspid valve size, presence of tricuspid insufficiency, presence of a patent ductus arteriosus, postoperative oxygen saturations, and atrial pressure gradients between the two groups. Evaluation of the left ventricular compliance in patients with pulmonary atresia and intact ventricular septum might be of significant prognostic valve for their early survival.