The t(3;21) (q26;q22) is associated with chronic myelogenous leukemia in blast crisis, leukemia evolving from therapy-related myelodysplasia, and with leukemia following other hematopoietic proliferative diseases. The t(3;21) is rare secondary aberration in blast crisis of Philadelphia(Ph)-positive chronic myeloid leukemia, which may be restricted to patients entering myeloid blast crisis. We report here in one case of chronic myeloid leukemia in blast crisis which reveals both t(9;22) (q34;q11), and t(3;21) (q26 ;q22). A 62-year-old male was diagnosed as chronic myeloid leukemia 5 years ago, received hydroxyurea therapy, and admitted because of gingival bleeding and fever. On examination, splenomegaly and leukocytosis with proliferated blasts(91%) in peripheral blood were noted. Bone marrow aspirate showed hypercellularity with severe blast proliferation(92.5%) which revealed all negative in peroxidase and PAS stain. Cytogenetic study of bone marrow cells showed the karyotype 46, XY, t(3;21) (q26;q22), t(9;22) (q34;q11), which might be suspected as myeloid blast crisis. Above finding was confirmed by the result of immunophenotyping(CD13 43.6%, CD34 68.2%, HLA-DR 91.6%). He received intensive chemotherapy, but still sustained proliferation of blasts was noted . The follow up cytogenetic study was as follows: 46, XY, 4(3;21) (q26:22), t(9;22) (q34;q11)/46, XY, t(3;21)(q26;q22), del(8) (q22), t(9:22) (q34,q11)/46, XY (16/3/1). He died soon from severe pancytopenia and sepsis.