Immunophenotypes of chronic myelogenous leukemia(CML) in chronic phase and in blastic crisis were reviewed. CML cells in chronic phase show a relatively mature immunophenotypes, such as CD13, CD33, CD15, and MPO, but not positive for CD34, CD117, TdT, and HLA-DR. When a CML transforms into blastic crisis, the blast cells demonstrate an immature myeloid(acute myelogenous leukemia(AML)-like) phenotypes in 60-70% of cases. The blast cells which have myeloid markers show CD13, CD33, MPO. In contrast to de novo AML, these myeloid blast cells often express megakaryocytic, erythroid markers or natural killer cell markers, and in some of the cases, the myeloid blast cells have complex phenotypes, with co-expression of markers from two or three lineages. The blast cells, in 25-30% of cases, demonstrate lymphoid blast phenotype characteristics similar to acute lymphoblastic leukemia(ALL), common ALL, or pre-B-ALL. In 60-80% of cases, the lymphoid blast cells co-express myeloid phenotype, fulfilling the criteria of biphenotypic leukemia.