Carbon tetrachloride and Dimethylnitrosamine, both potent hepatotoxic agents, affect the hepatic lobules with fatty changes and central necrosis, and hemorrhagic necrosis. To study the effects on morphologic changes of the hepatic lobules in cases of single and repeated treatment of both hepatotoxins, sublethal doses of carbon tetrachloride, 0.4ml/kg, and dimethylnitrosamine, 40mg/kg of rats were given intraperitoneally single, twice and triple. With interval of 3 days, and the results were as follows : 1. The fatty changes and central necrosis of the hepatic lobules were milder and more quickly disappeared in the rats with twice or triple treatment than single administration of carbon tetrachloride, and regenerative changes of hepatic and sinusoidal cells achieved fater in the rats with repeated administration of carbon tetrachloride than those with single treatment. 2. The hemorrhagic necrosis of the hepatic lobules was not significantly influenced by the times of DMN treatment, but the hyperplastic changes showed more active to animals, with multiple administration of DMN.