Introduction Abuse of solvents containing hexane by children has generated a great deal of concern about the potential toxicities because so little is known about the effects of inhaled solvents at various stages of development [I]. Thus@ an evaluation of the neurotoxin effects of hexane at various ages is of particular importance |2J. Bus et al [3] showed that exposure of pregnant rats to 1000 ppm of hexane inhibited the postnatal growth of the pups@ but they found no evidence of teratogenicity. Kimura et al [4] reported that 14-day-oId last were more sensitive than adults to the acute toxic effects of hexane. We have found that weanling rats synthesize 2@5-hexanedione (2@S-HD)@ the apparent proximate neurotoxin [5]@ approximately as welt as adults [6]. This similarity in rates of synthesis of 2@5-HD is not surprising@ since many rat liver microsomal enzyme systems have reached adult levels by the age of weaning [7@ 8]. This result could mean that the susceptibility to hexane-induced neuropathy might be similar in weanlings and adults. We report here the results of exposing weanling and young adult rats concurrently to 1000 ppm of hexane continuously@ in order to compare the rate of development and seventy of effects at the two ages This rather intense schedule of hexane exposure was chosen so that the neuropathies would develop quickly@ while the weanling rats were still immature.