The diagnostic dilemma of the newborn with congenital heart disease must be resolved quickly because therapy may prove lifesaving for some of these infants. Congenital heart disease occurs in ∼1% of live-born infants. Nearly half of all cases of congenital heart disease are diagnosed during the first week of life. In patients with complex congenital heart disease, neonatal hospital mortality can be as high as 7%. These patients have a high frequency of multiple congenital anomalies, syndromes, low birthweight, and prolonged length of stay. The most frequently occurring anomalies seen during this first week are patent ductus arteriosus (PDA), D-transposition of the great arteries, hypoplastic left heart syndrome (HLHS), tetralogy of Fallot (TOF), and pulmonary atresia.