Reports concerning hexacarbon neurotoxicity in humans and animals are reviewed. N-hexane (110543) and methyl-n-butyl-ketone (591786) (MBK) are neurotoxic in humans following prolonged exposure. The mixing of hexacarbon solvents with other solvents in industrial facilities where protective devices, worker education, and ventilation are deficient results in human neuropathy. Insidious onset, a slow course, and continuous progression of disability following cessation of exposure are signs of industrial neuropathy, with complete recovery requiring 10 months to 3 years. Industrial exposure problems are compounded by the absence of an organized industrial hygiene program and the insufficient monitoring of worker health. Most cases of human hexacarbon neurotoxicity reported worldwide cite n-hexane or MBK as causal agents. The deliberate inhalation of solvent, lacquer, glue, or glue thinner vapors, known as glue sniffing, is the most common cause of human hexacarbon neuropathy. All documented cases of neuropathy due to glue sniffing relate to n-hexane, which is usually present in conjunction with other six carbon compounds. One such study indicates that the n- hexane concentrations in place in the air when using a plastic bag to inhale solvent vapors can reach 44,000 parts per million (ppm). Brief exposures to n-hexane concentrations ranging from 1,400 to 2,000ppm cause nausea, headaches, and eye and throat irritation, while a concentration of 5,000ppm inhaled for 10 minutes results in giddiness and mild narcosis. Other symptoms include proximal weakness, respiratory insufficiency, cranial nerve palsy, and greatly slowed nerve conduction velocities. Respiratory, subcutaneous or intraperitoneal exposure to n-hexane or MBK induces neurological damage in experimental animals. Inhaled MBK has a much greater neurotoxic effect on human and animal subjects than n- hexane. The MBK exposure concentration limit currently in force in the United States is 1ppm, while the same value for n-hexane is 100ppm. Threshold limits established for these substances by the American Conference of Governmental and Industrial Hygienists are 5 and 25ppm, respectively.