Discussion of a curious disease of the blood was begun by Copelli in 1912 and continued by di Guglielmo. Dameshek and Gunz called it the "di Guglielmo syndrome" and defined it as a "myeloproliferative disorder". This syndrome is a condition characterized principally by neoplastic proliferation of the cells of the erythroid series, which is frequently, if not invariable, associated with leukemic proliferation of the cells of the granulocytic series. Many studies and clinical observations had been reported in the western and Korean(38 cases) literature. About 10 cases of the 38 cases are complete regarded to develop a final stage of acute leukemia. This report describes 5 cases of di Guglielmo's syndrome.