This study was undertaken to investigate the toxic effect of AF-2, 2-(2-furyl)-3-(5-nitro-2-furyl) acrylamide, in the diet of rats (Splague Dowley) for 4 weeks. Comparisons were made of weight gains, organ weights and the cholesterol, phospholipid and triglyceride content of the blood serum and liver tissue. Rats were divided into three groups, a control group which was fed on a standard diet and two groups were fed with 0.04% (group I) and 0.2% (group II) of AF-2. Male rats weighing 370-410 g, female rats weighing 240-250 g were used in this experiment and each group was composed of 24 Albino rats. The results were as follows. 1. Comparisons of weight gains, control and experimental groups did not show significant differences. 2. An examination of organ weights, liver weights of experimental groups showed higher than that of the control group. 3. In the lipid content of blood serum, phospholipid contents of experimental groups were lower than that of the control, while cholesterol and triglyceride content of experimental groups were higher than that of the control. 4. In the lipid content of liver tissue, phospholipid and triglyceride content of experimental groups did not show considerable changes, but cholesterol content was increased in proportion to AF-2 content. From these results, the authors could observe the significant changes in weight gains of liver and cholesterol content after feeding. It is concluded that the toxic effect of group II showed higher than that of group I and AF-2 had a toxic effect on rat liver to a certain extent.