Advances in surgical technique and postoperative care have resulted in substantial improvement in the operative mortality after repair of atrioventricular canal defects. However, significant late morbidity and the need for reoperation complicate the medium and long-term results in these patients. Left atrioventricular valve regurgitation, residual or recurrent intracardiac shunting, and subaortic stenosis are the principle causes of late morbidity after repair of complete and partial atrioventricular canal defects. This article describes the incidence and etiology of these complications, as well as the methods of diagnosis and management.