In order to investigate the acute toxicity of autoxidized methyl linoleate(AOML) on the activity of serum enzymes in the mouse, we administered once 0.45ml of AOML to ICR strain mouse by using stomach tube. The following results were obtained: The total lactic dehydrogenase(LDH) activities in the serum of AOML group were generally increased than those of mormal group. According to electrophoresis, the activities of LDH, were increased while those of LDH, were decreased. The activities of glutamic oxaloacetic transaminase(GOT), glutamic-pyruvic transaminase(GPT) and α-amylase in the serum of AOML group were increased more than those of mormal group. The activities of alkaline phosphatase in the serum of AOML group were increased but those of isozyme were not confirmend in the normal and AOML group. In the serum protein of AOML group, albumin was increased, on the other hand r-globulin was decreased. At the peripheral blood slide smear, lymphocytes were significantly decreased but neutrophils were increased and the morphological change of erythrocytes was observed. From these results we conclude that the AOML fed to mouse influences on the activity of various serum enzymes and blood cells in the mouse.