Objectives: Cross-sectional studies of intermediate-term survivors of infant cardiac surgery have revealed a high frequency of neurodevelopmental disabiliti es. Few data exist regarding neurodevelopmental outcome of infants undergoing su rgical intervention for a ventricular septal defect. The purpose of this study w as to evaluate the neurodevelopmental outcome at 1 year of age of children who h ad surgical repair in infancy of a ventricular septal defect or a ventricular se ptal defect with aortic arch obstruction. Methods: Children who underwent repair of a ventricular septal defect or single-stage repair of a ventricular septal defect with aortic arch obstruction at less than 6 months of age were assessed a t 1 year of age by using the Bayley Scales of Infant Development II, which yield s the Mental Development Index and the Psychomotor Development Index, both with an expected mean of 100±15. Results: At 1 year, 55 patients(ventricular septal defect alone=36; ventricular septal defect with aortic arch obstruction=19) retu rned for evaluation. The mean Mental Development Index was 92.6±11.7, with 3(5 %) patients scoring 70 or less. The mean Psychomotor Development Index was 86.1 ±16.4, with 10(18%) patients scoring 70 or less. Patients with a suspected or confirmed genetic syndrome had both a lower Mental Development Index score(P=.01 1) and a lower Psychomotor Development Index score(P=.001). Mental Development I ndex and Psychomotor Development Index were independent of anatomic(specifically aortic arch obstruction) and intraoperative factors(specifically deep hypotherm ic circulatory arrest). Conclusions: Neurodevelopmental outcome at 1 year of age was within the normal limits for most patients who underwent repair of a ventri cular septal defect or a ventricular septal defect with aortic arch obstruction during infancy. Objectives: Cross-sectional studies of intermediate-term survivors of infant cardiac surgery have revealed a high frequency of neurodevelopmental disabiliti es. Few data exist regarding neurodevelopmental outcome of infants undergoing su rgical intervention for a ventricular septal defect. The purpose of this study w as to evaluate the neurodevelopmental outcome at 1 year of age of children who h ad surgical repair in infancy of a ventricular septal defect or a ventricular septal defect with aortic arch obstruction. Methods: Children who underwent repair of a ventricular septal defect or single-stage repair of a ventricular septal defect with aortic arch obstruction at less than 6 months of age were assessed at 1 year of age by using the Bayley Scales of Infant Development II, which yield the the Mental Development Index and the Psychomotor Development Index, both with an expected mean of 100 ± 15. Results: At 1 year, 55 patients (ventricular septal defect alone = 36; ventricular septal de The mean Mental Development Index was 92.6 ± 11.7, with 3 (5%) patients scoring 70 or less. The mean Psychomotor Development Index was 86.1 ± 16.4, with 10 (18% ) patients scoring 70 or less. Patients with a suspected or confirmed genetic syndrome had both a lower Mental Development Index score (P = .01 1) and a lower Psychomotor Development Index score (P = .001). Mental Development Index and Psychomotor Development Index were independent of anatomic (specifically aortic arch obstruction) and intraoperative factors (specifically deep hypothermic ic circulatory arrest). Conclusions: Neurodevelopmental outcome at 1 year of age was within the normal limits for most patients who underwent repair of a ventri cular septal defect or a ventricular septal defect with aortic arch obstruction during infancy.