Long-standing pulmonary insufficiency after repair of tetralogy of Fallot may adversely affect ventricular function. We evaluated 20 patients postoperatively by radionuclide ventriculography and clinical findings after total correction of tetralogy of Fallot. Patients were divided into two groups as follows: Group I patients (10) had no pulmonary insufficiency; Group II patients (10) had moderate or severe pulmonary insufficiency. Preoperatively, there was no difference between groups in terms of age, functional capacity according to the New York Heart Association criteria, hemoglobin and hematocrit level, cardiothoracic ratio, McGoon ratio, left and right ventricular ejection fraction, cardiac output or cardiac index. Postoperatively, right ventricular ejection fraction was 40.10 +/- 2.28 in Group I and 29.5 +/- 2.86 in Group II, p < 0.01. Left ventricular ejection fraction was 59.3 +/- 2.90 in Group I and 50.9 +/- 4.19 in Group II, p < 0.01. Radionuclide ventriculography is a useful means of identifying right ventricular dysfunction following repair of tetralogy of Fallot. The dysfunction appears significantly worse in patients with pulmonary insufficiency.