This testimony summarized information dealing with worker exposure to neurotoxic chemicals. Following a definition of neurotoxicity, the testimony described some of the investigations on workers exposed to such chemicals on the job in which NIOSH has been involved. Included among the examples were the workers in Hopewell, Virginia, exposed to kepone (143500), who suffered loss of muscle coordination, loss of memory, and an eye movement disorder. Another episode of workers exposed to a pesticide involved leptophos (21609905). At the time of the exposure, leptophos was registered by the Environmental Protection Agency primarily for export. Animals administered a single oral dose showed weight loss, ataxia, and eventual muscle paralysis. Other potentially toxic chemicals were used in the preparation of leptophos including toluene (108883), a neurotoxic solvent. A third incident of worker exposure to pesticides occurred due to the release of o-ethyl-o-p- nitrophenylphenylphosphonothioate (2104645) (EPN), at a manufacturing site in Chicago Heights, Illinois. Neurological signs of distress included muscle weakness and cerebellar signs of toxicity. Cases of worker exposure to the following solvents were also reviewed: methyl-n-butyl-ketone (591786) and carbon-disulfide (75150). Exposures to metals were also reviewed including lead (7439921), arsenic (7440382), and mercury (7439976). Early detection of exposures to neurotoxic agents was briefly considered.