The clinical and necropsy findings in 3 patients with tetralogy of Fallot who died suddenly after corrective operation are presented. Early postoperative electrocardiograms of 2 patients showed coexistent right bundle-branch block and left anterior hemiblock; one of these developed complete atrioventricular block and required a pacemaker. In the third a pacemaker. In the third patient, postoperative electrocardiograms showed anterior myocardial infarction. At necropsy, there was gross and histological evidence of myocardial infarction in each patient. After operation, extensive myocardial fibrosis and the development of right bundle-branch block and left anterior hemiblock are possible factors causing cardiac arrhythmias and sudden death.