The neurotoxic effects of organic solvents are reviewed. Organic solvents have been used in extraction, dissolution or suspension of fats, waxes and resins. Studies have shown that acute neurotoxicity is similar for human and laboratory animal exposures and is characterized by narcosis, anesthesia, central nervous system depression, respiratory arrest, loss of consciousness and death. Chronic effects have been studied to a limited extent in animals and have been documented epidemiologically for workers and solvent abusers. Reported effects included peripheral neuropathy and mild toxic encephalopathy. Three severity levels were defined for chronic human exposures: minimal, organic affective syndrome; moderate, mild, chronic toxic encephalopathy; and pronounced, severe, chronic toxic encephalopathy. Neurophysiological effects (electromyogram or electroencephalogram abnormalities, decreased nerve conduction velocities) have also been reported in exposed workers. Neurobehavioral effects such as reversible subjective symptoms, prolonged personality or mood changes and intellectual impairment have been studied epidemiologically and in volunteers. Severe exposure has produced irreversible impairment of intellect and memory (dementia) and structural central nervous system damage. Metabolic aspects of organic solvent exposure were discussed. Guidelines for minimizing worker exposure are discussed in relation to exposure monitoring; control of exposure through contaminant control, worker isolation, use of personal protective equipment and worker education; and medical surveillance. A table containing a summary of NIOSH recommended exposure limits for organic solvents is presented. Examples of solvents neurotoxic to humans discussed include carbon-disulfide (75150), n-hexane (110543), methyl-n-butyl- ketone (591786), trichloroethylene (79016), perchloroethylene (127184) and toluene (108883).