Clinical and pathologic features of the case of an 11-year-old boy who underwent operative repair of tetralogy of Fallot nine months before death are described. Aortic regurgitation was produced inadvertently at operation during an unsuccessful patch closure of the ventricular septal defect. Postoperatively, the child developed severe cardiac failure and mild anemia. During a second operation seven days before death, aortic blood, which regurgitated through the aortic valve, was observed to contact the nonendothelialized ventricular septal patch, which only partially closed the septal defect. Erythrocytes were traumatized by the jet of blood contacting the nonendothelialized patch, liberating free hemoglobin, which was filtered by glomeruli and reabsorbed by renal tubules (renal hemosiderosis). Intravascular hemolysis after patch closure of ventricular septal defect has not been described previously.