The data has been collected by the Australian and New Zealand neonatal Network (ANZNN) to improve the care of high-risk newborn infants and their families in Australia and New Zealand through collaborative audit and research. The data were collected from all level III neonatal intensive care units in both Australia and New Zealand, all level II special care units in New Zealand and the special care unit in Tasmania. The data include information on all babies born at less than 32 weeks gestation or with a birthweight of less than 1500 grams and babies who received assisted ventilation or major surgery. In 2005, There were 6,044 babies registered to ANZNN from 22 NICUs in Australia and 1,585 babies registered at all level III NICUs in New Zealand. In level II nurseries, 411 babies fulfilled the ANZNN criteria and registered with ANZNN. Data in this collection include: maternal characteristics (maternal age, gestational age, presenting antenatal problem, antenatal corticosteroid use, method of delivery, place of birth, transfer after birth to a level III NICU, and plurality of birth ); and baby's characteristics (admission temperature, apgar score at birth, exogenous surfactant, respiratory assistance, type of assisted ventilation, chronic lung disease, air leak, retinopathy of prematurity, cerebral ultrasound and necrotising enterocolitis, neonatal surgery, neonatal infection, congenital anoamlies, breast feeding at discharge, transfer from level IIl NICUs to other nurseries and length of stay until discharge home, discharge status).