To investigate the incidence of neoaortic insufficiency in patients with hypoplastic left heart syndrome treated with the Norwood-Sano palliation and to compare it with that occurring after the classic Norwood procedure.This was a retrospective review of all echocardiograms of patients diagnosed with hypoplastic left heart syndrome (concomitant presence of left ventricular and aortic and mitral severe hypoplasia or atresia) who underwent staged palliation of the Norwood or Norwood-Sano type at a single academic institution between September 1999 and February 2005 and who survived a minimum of 3 months.Neoaortic insufficiency was categorized as absent or mild 3 mm jet width. The patients were grouped according to initial palliation, that is, classic Norwood and Norwood-Sano operation.Fifty-nine consecutive patients (median age of 20 months with a range from 3 to 66 months) satisfied inclusion criteria. Neoaortic insufficiency was absent or mild in 55 of 59 (93.22%) of the patients. There were 4 cases of significant neoaortic insufficiency at late follow-up: 2 moderate following the classic Norwood and 1 moderate and 1 severe following the Norwood-Sano procedure, one of whom required valve replacement.In this series of patients with hypoplastic left heart syndrome, the Sano modification was not associated with an increased incidence of significant neoaortic insufficiency. When present, moderate/severe neoaortic insufficiency appeared late after initial palliation and was associated with recurrent ascending aortic or aortic arch pathology in every case.