Aim: To describe neurodevelopmental outcomes of neonates following cardiac or non-cardiac surgery for major birth defects. Methods: From 1 June 2002 to 31 July 2004, infants born ≥33 weeks gestation who underwent major birth defect surgery were enrolled prospectively. Infants were assessed at amean corrected age of 24 months (standard deviation (SD) = 8 months, range 18-36 months) using the Bayley Scales of Infant Development: Second Edition. Results: Of the 118 study infants, 79 (66%) were male, the mean gestation was 38.5 weeks (SD 1.9 weeks) and mean birthweight was 3194 g (SD 653 g). Forty-five infants (47%) had undergone general surgery for non-cardiac defects. The majority of infants (73%) performed belowaverage in cognitive and language skills. Mental delay was found in 41% of infants; 16% were significantly delayed. Fine and gross motor skills were below average in 60% of infants. Twenty-six percent of infants had motor delay; 9% were significantly delayed. Both the mean Mental Development Index (M = 88, SD = 19.8) and mean Psychomotor Development Index (M = 93, SD = 19.3) were significantly below the normative mean (d = 0.8, P < 0.001 and d = 0.5, P < 0.001, respectively). One in five children had global developmental delay. There was no significant difference in outcome between the cardiac and general surgery groups. Conclusions: The majority of infants performed below average on a standardised test of infant development. Our results show that infants requiring newborn surgery for major birth defects are at high risk of adverse neurodevelopmental outcomes. We recommend that follow-up programmes include systematic multidisciplinary developmental monitoring and early intervention.