Comparative studies on histone from normal leukocyte and chronic myelocytic leukemic granulocyte were done. Five main fractions of histone were obtained by the method of Johns. And each of the fractions was confirmed of its homogeneity and its distinct electrophoretic mobilities on polyacrylamide gel electrophoresis. Total amounts of histone isolated from normal and leukemic cells were 37.08 mg and 58.64 mg per one gram of packed cells, respectively. Relative yields of histone fractions of leukemic cells revealed marked increment of f2b fraction and concurrent decrements of f1 and f3 fractions as compared to those of normal WBCs. Phenylalanine was increased, and arginine and glycine were decreased in f1 fraction of leukemic cells as compared to those of normal WBCs. Ratio of acidic to basic amino acids was not changed but the ratio of arginine to lysine was changed from 4.05 in f1 of normal WBCs to 11.85 in that of leukemic cells. F2b of leukemic cells contained lesser amount of isoleucine, and f3 of leukemic cells contained higher amount of histidine, as compared to that of normal WBCs, respectively. The composition of amino acids of f2a1 and f2a2 from leukemic granulocyte was similar to that of normal WBCs. $epsilon$-N-mono- and $epsilon$-N-dimethyllysine were observed in f3 of leukemic cells, which was not observed in normal WBCs. As methylase activity is increased in cancerous cell in general, the presence of methylated derivatives of lysine in leukemic cells in contrast to the absence of methylated derivatives in normal WBCs may have significant meanings.