The aEEG was recorded as a single channel EEG from biparietal surface disk electrodes using a CFM (CFM 5330, Lectromed Devices Ltd., UK) or the CFM 6000 (Olympic Medical, USA). Assessment of neurodevelopmental outcome was done at three years of age by assessment of the Bayley Scales of Infant Development II (BSID-II) During the study period from January 1st 2000, and December 31st 2002 a total of 284 preterm infants less than 30 weeks´ gestational age were admitted to the neonatal intensive care unit of the Medical University of Vienna. Neurodevelopmental outcome could be obtained in 148/284 infants at the age of three years and these infants therefore fulfilled the inclusion criteria for this study