A wealth of experience has been gained in the management of atrioventricular septal defect (AVSD) since the first complete correction of this malformation in 1955. The success of surgical therapy followed an enhanced understanding of morphology and physiology as well as major improvements in imaging of this congenital heart defect. Therapeutic success in the management of patients with AVSD has been extended to include those with associated lesions such as tetralogy of Fallot, double outlet right ventricle and relative degrees of ventricular hypoplasia. Although operative mortality is low and long-term survival is relatively good, important detrimental residual or AVSD-related complications such as left atrioventricular valve regurgitation, left ventricular outflow tract obstruction still carry significant late morbidity in a proportion of patients. This article reviews our current understanding of the morphology of this defect, aspects of diagnosis and surgical treatment options.