Acrylamide was tested for chronic toxicity and oncogenicity in Fischer 344 rats (90/sex/dose level) fed nominal doses of 0, 0.01, 0.1, 0.5, or 2.0 mg/kg bw/day in the drinking water for 2 years. In groups given 2.0 mg/kg/day, there was significantly increased mortality (beginning about the 21st month) and degeneration of the peripheral nerves. In females given 2.0 mg/kg/day, tibial nerve degeneration was observed. Other parameters of food and water consumption, clinical chemistry, organ weights, and organ/body weight ratios were not consistently affected by the treatment. A significantly increased tumor incidence at the 2.0 mg/kg/day dose level was reported for the following sites: females; mammary gland (benign and malignant), pituitary gland, central nervous system (malignant), clitoral gland (benign), uterus (malignant), and the oral cavity (benign); males and females; the thyroid gland (malignant and benign). The incidence of scrotal mesothelioma (malignant) was also significantly increased in male rats given 0.5 mg/kg/day.