In order to investigate the role of ''neurosteroids'' in the central nervous system (CNS), cerebrospinal fluid (CSF) levels of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) were determined by radioimmunoassay in 57 patients with various neurologic disorders and 26 patients with non-neurologic disorders. The content of CSF DHEA and DHEAS in patients with Guillain-Barre syndrome (GBS), and the content of CSF DHEAS in patients with carcinomatous meningitis were significantly higher as compared to non-neurological control patients. These changes may be explained by the breakdown of blood-nerve barrier in these disorders. A significant positive correlation was observed between DHEAS and total protein in CSF. In males but not females, a negative correlation was observed between CSF DHEAS and aging. The level of CSF DHEAS, but not DHEA, was significantly higher in males than in females.