Effect of fluorescent products from the reaction of malonaldehyde with dipalmitoyl phosphatidylethanolamine on the content of lipids in plasma and liver of rats was examined, and the results are as follows: Growth of rats was suppressed by daily intraperitoneal administration of fluorescent products (10 or 50 mg/kg) for 7 days. Levels of triglycerides and total cholesterol in the plasma tended to decrease but that of phospholipids increased significantly by the administration of fluorescent products in a dose of 50 mg/kg/day. On the other hand, content of triglycerides in liver decreased by about 26% at a dose of 10 mg/kg and 23% at a dose of 50 mg/kg. Total cholesterol and phospholipids showed a slight diminution. Free fatty acid content in the liver was almost constant. Thiobarbituric acid values in the plasma and liver increased significantly by treatment with the fluorescent products, especially the values at a rate of increase were higher in the plasma than in the liver. No significant changes were observed in the relative fluorescence intensity between control animals and groups treated with fluorescent products. Serum lipoprotein patterns after Agarose gel electrophoresis revealed diffuse bands in the pre-beta and beta-regions.