Abstract Forty patients required reoperation after corrective surgery for tetralogy of Fallot. Indications for reoperation included residual ventricular septa I defect (VSD) with Q p Q s > 2:1 , right ventricular outflow gradient (ΔP) of 60 mm. Hg or more, and aneurysm of the right ventricular outflow tract. VSD alone was found in nine patients (22.5 percent) and ΔP alone in seven patients (17.5 percent). VSD and ΔP occurred together in an additional 19 patients (47.5 percent). In 19 of the 29 patients with VSD, disruption of the patch suture line was located at the posteroinferior quadrant. Five patients had a right ventricular aneurysm; all had ΔP and one also had a VSD. An outflow patch had been placed at the first operation in four of the five. Thirty-eight patients (95 percent) survived: complete heart block occurred in one patient; transection of an anomalous descending coronary artery led to myocardial infarction and chronic heart failure in another. Twenty patients have been recatheterized. Two have a residual VSD and three a residual gradient of 40, 50, and 70 mm. Hg, respectively. Reoperation for residual lesions after tetralogy repair can be associated with mortality and morbidity rates no greater than with the original operation.