AIM: The aim of the study was to compare neurodevelopmental outcomes of extremely preterm infants admitted during (OH) and after (AH) office hours. METHODS: A retrospective review of the New South Wales and Australian Capital Territory Neonatal Intensive Care Units' (NICUs) Data Collection of all infants <29 weeks gestation admitted to New South Wales and Australian Capital Territory NICUs between January 1998 and December 2004 was conducted. The primary outcome was moderate/severe functional disability (FD) at 2-3 years follow-up defined as developmental delay (Griffiths Mental Developmental Scales general quotient or Bayley Scales of Infant Development-II mental developmental index >2 standard deviations below the mean), cerebral palsy (unable to walk without aids), deafness (requiring bilateral hearing aids) or blindness (visual acuity <6/60 in the better eye). RESULTS: Mortality and age at follow-up were comparable between the AH and OH groups. Developmental outcome was evaluated in 972 (74.9%) infants admitted during AH and 501 (74.6%) admitted during OH. FD was not significantly different between the AH and OH groups (17.1% vs. 14.8%, adjusted odds ratio 1.131, 95% confidence interval 1.131 (0.839-1.523), P = 0.420). There were no significant differences between AH and OH infants with cerebral palsy (9.6% vs. 7.6%), developmental delay (5.4% vs. 5.0%) or any other component of FD. CONCLUSION: There is little circadian variation in mortality and adverse neurodevelopmental outcomes in an NICU network with the current model of after hours staffing and support, and sharing of NICU workload within a network.