Glial fibrillary acidic protein (GFAP) is the structural protein of the intermediate filament of astroglia. The aims of the present study were to examine GFAP in the cerebrospinal fluid (CSF) of preterm infants at different postmenstrual ages and to evaluate the potential of GFAP to predict abnormal neurodevelopmental outcome. GFAP increased in correlation with postmenstrual age in preterm infants (n = 17) and full-term infants (n = 9). The levels were five times higher in preterm infants (n = 10) with an abnormal neonatal course and/or an abnormal neurological outcome than in healthy preterm infants. The positive predictive value of a GFAP higher than the 98th percentile of normal infants was 69%, while a GFAP level below this limit invariable predicted a good outcome. Simultaneously analysed noradrenaline, hypoxanthine and glutamate did not differ between the groups. We conclude that CSF GFAP increases with maturity and that CSF GFAP appears to be a promising marker for perinatal brain damage.