Nuclei proteins were purified from chick liver to homogeneity by means of acid extraction CM Sephadex c 25 column chromatography and Bio Rex 70 column chromatography, The molecular weight of liver Nuclei proteins 1 and 2 as estimated by electrophoresis on SDS-polycrylamide gel are 29000 and 27,000 respectively. These molecular weights are identical with those of Nuclei Proteins 1 and 2 isolated from chick erythrocyte. The liver and erythrocyte Nuclei Proteins also co-migrated in acetic acid-urea gel electrophoresis. Furthermore the anti-sera raised against liver Nuclei Proteins 1 and 2 cross-reacted with erythrocyte Nuclei Proteins 1 and 2 respectively, However the amino acid compositions of liver Nuclei Prooteins 1 and 2 were found to be different from those of corresponding erythrocyte Nuclei proteins ; the contents of serine and proline in liver Nuclei proteins were higherocyte Nuclei proteins ; the contents of serine and proline in liver Nuclei protesins were higher than those in erythrocyte Nuclei proteins while the content of lycsine in liver Nuclei proteins was lower than the erythrocyte Nuclei proteins, These results suggest that in spite of similarities in many respects the liver and erythrocyte Nuclei proteins in chicks and different proteins.