Repeated oral administration of an amine-curing agent for epoxy resin, bis(4-amino-3-methylcyclohexyl)methane, gave rise to severe damage in the choroid plexus of rat brain. The damaged epithelium presented varying degrees of swelling and hydropic vacuolation on light microscopy, and varying numbers of vacuoles and inclusion bodies, frequently with lamellar structure, on transmission electron microscopy. Scanning electron microscopy of the choroid plexus disclosed some irregularity in the size of epithelial cells and occasional loss of microvilli. These changes in the choroid plexus were closely correlated with the dosage of the agent administered and the period of administration. In spite of the severe changes in the choroid plexus, no neurological abnormalities were observed in the animals during the experimental period.