Cerebrospinal fluid was examined for 23 patients with chronic toxic encephalopathy after heavy exposure to organic solvents and 23 healthy age-matched referents. No differences were found between the patients and referents with respect to the levels of albumin, immunoglobulin, prealbumin, alpha-1-antitrypsin, beta-2-microglobulin, haptoglobin, or the astroglial cell proteins S100 and glial fibrillary acidic protein in the cerebrospinal fluid. The albumin ratio was normal for both the patients and the referents. The patient group had had heavy exposure to organic solvents, but its members had not been exposed for at least one year before the study. It was concluded that, if exposure to organic solvents affects proteins in cerebrospinal fluid, such effects are probably reversible.