Tremendous gains have been made in recent years in the diagnosis and management of congenital heart malformations. Recognition of cardiac pathology is an imperative first step in the treatment of the newborn infant with critical congenital heart disease. This review will focus on the following: (1) a description of the forms of critical neonatal heart disease, including left heart obstructive lesions and pulmonary blood flow obstructive lesions and (2) a review of the clinical symptoms of ductal-dependent left heart obstructive lesions. This summary is limited to those conditions that present early in the neonatal period and require prompt intervention. Identification of affected infants before discharge and prompt initiation of prostaglandin therapy is life-saving in this population.