Complete atrioventricular septal defect (AVSD) has a common atrioventricular (AV) junction with a common AV orifice, a trifoliate left AV valve with a common fibrous ring, partially shared valve leaflets, a large primum ASD and a variable inlet VSD. The common AV valve has five leaflets. Attachment of the superior bridging leaflet to the right side forms the basis of Rastelli classification. Left ventricular outflow (LVOT) is vulnerable to obstruction. Lack of AV septal structures and the central fibrous body lead to abnormal AV conduction. Clinical features depend upon size of VSD and severity of AV valve regurgitation. Common presentations are heart failure and frequent respiratory infections. S2 is widely split with loud P2, S3 (LV or RV) is present with a pulmonary ejection click and pan-systolic murmur over apex conducted to left sternal border. Down’s syndrome is a common association. Irreversible pulmonary vascular disease develops early. ECG shows superior axis with counter clockwise depolarization, prolonged PR interval, left and/or right atrial enlargement, incomplete RBBB pattern and left ventricular hypertrophy. Chest X-Ray shows cardiomegaly and increased pulmonary vascularity. Echocardiographic features are a large single AV orifice, four chamber view shows primum ASD, inlet VSD and the AV valve regurgitation. Catheterization is indicated to assess reversibility in presence of pulmonary vascular disease, when associated defects are present and when a univentricular pathway is being contemplated. LV angio shows the typical gooseneck deformity of the LVOT. Early corrective surgery is the definitive way of management.