The author produced splenomegaly in rabbits by the successive injections of non-physiological macromolecular polymers, and obtained the following results. 1) By the successive injections of methylcellulose, polyvinylalcohol, and ovalbumin either intravenously or intraperitoneally for the periods ranging 50-100 days, the author obtained hematologic macromolecular syndrome, marked anemia and thrombocytopenia in the rabbits. 2) Bone marrow picture revealed the inhibition of maturation in the erythroid system. 3) All the groups receiving injections demonstrated splenomegaly and an increase of the blood pressure in the portal vein. Histologic findings of the spleen were the marked proliferation of reticular cells and occasionally the picture which seems to be fibroadenia. 4) Serum iron decreased while serum copper increased on the contrary. However, the depot iron maintained the normal level. In tracing the mechanism of this experimental anemia from the fact that the depot iron did not decrease despite the marked decrease of the serum iron, the author concluded that the principal cause of this experimental anemia lies in the inhibitory action of toxic factor upon the mobilization of depot iron. The results of this experimental hypersplenism are believed to be identically the same as those of so-called Banti's disease as reported by T. Kobayashi.