We have reviewed our experience with 61 infants with the hypoplastic left heart syndrome and conclude that for approximately one half, salvage by intensive medical management and surgical palliation is possible. Provided that cardiac catheterization and selective angiocardiography demonstrate adequate blood flow in the ascending and transverse aortic arch, palliation may be accomplished by relief of pulmonary venous obstruction and, if necessary, the conversion of either excessive or diminished pulmonary arterial flow to an adequate amount. The hypoplastic left heart syn¬ drome1 is a common anomaly which accounts at the present time for most of the deaths due to con¬ genital cardiac malformations in the first months of life.110 We include under this designation these abnor¬ malities marked by underdevelopment or absence of one or several anatomic characteristics of the left side of the heart: atresia or hypoplasia of the left atrial outlet, the left ventricle, the aortic valve, and arch. Localized or diffuse hypo¬ plasia of the transverse aortic arch is often found together with one or more of the previously named abnor¬ malities. We have reviewed the clinical data and the anatomic specimens of the 58 examples of these forms of the hypoplastic left heart syndrome which are in the postmortem collec¬ tion of congenital heart defects at