Nerve growth factor (NGF) in cerebrospinal fluid was measured by ELISA in ten children with postinfectious diseases and in five children with diseases suggested to be of autoimmune etiology, Three groups of patients were studied: (1) those with moderately elevated concentrations (50.67 +/- 17.02 pg/mL, mean and SEM), (2) those with high concentrations (mean 424.25 +/- 125.41 pg/mL, mean and SEM), and (3) those with enormously high concentrations (mean 2,745 +/- 1,819.46 pg/mL, mean and SEM). We suggest that CSF-NGF could be used as an immunologic marker of an ongoing CNS process, Uncontrolled signaling of NGF receptors may lead to long-term inflammatory and autoimmune responses, which in turn can lead to disease. (C) 1998 by Elsevier Science Inc. All rights reserved.