Oral administration of methacrylonitrile to male Wistar rats at a dose of 40 mg/kg body weight/day (LD50, 200 mg/kg body weight/day) for 2 weeks caused an increase in blood glucose levels with a depletion of liver glycogen. An increased rate of glycolysis and enhanced glycogenolysis and gluconeogenesis, along with the activation of the hexose monophosphate pathway shunt, were observed, indicating a significant disturbance in the carbohydrate metabolism.