Brain derived neurotrophic factor (BDNF) is a neurotrophic factor that is relatively highly expressed in developing and adult brain. Whereas clinical determinations of nerve growth factor (NGF) in human serum and cerebrospinal fluid (CSF) in different conditions have been undertaken there are no reports on levels of BDNF in human CSF. Here we show that BDNF is increased in CSF of neonatal children suffering from asphyxia which is characterised by periods of brain hypoxic-ischemia. In contrast to BDNF, levels of CSF NGF were largely decreased in these children. The present results show that BDNF can be detected in human CSF and that the levels increase following hypoxic-ischemic brain injury. As suggested by animal studies the increased BDNF might counteract neuronal damage observed in these patients following asphyxia. (C) 1998 Elsevier Science Ireland Ltd.