The effects of repeated intraperitoneal administration of aflatoxin B1 on the peripheral and central nervous systems of rats were investigated. Biochemical markers of neurotoxicity were monitored in nervous tissues following aflatoxin B1 dosage and after the cessation of aflatoxin B1 administration. Aflatoxin B1 increased the activities of beta-glucuronidase and beta-galactosidase in the central and peripheral nervous systems. Repeated exposure of rats to aflatoxin B1 also activated Na+ K+-ATPase and inhibited Mg2+-ATPase. Nervous tissue levels of DNA and total protein increased while the concentrations of RNA and phospholipid were depressed by aflatoxin B1. The alterations in these parameters were specific for each of the tissues examined during the recovery of the rats. The findings indicate that the repeated administration of aflatoxin B1 to rats results in degeneration in the central and peripheral nervous systems that may be related to the overt toxicity observed following aflatoxin administration.