Expression of the 210-kD bcr/abl fusion oncoprotein can cause a chronic myelogenous leukemia (CML)-like disease in mice receiving bone marrow cells transduced by bcr/abl-encoding retroviruses. However, previous methods failed to yield this disease at a frequency sufficient enough to allow for its use in the study of CML pathogenesis. To overcome this limitation, we have developed an efficient and reproducible method for inducing a CML-like disease in mice receiving P210 bcr/abl-transduced bone marrow cells. All mice receiving P210 bcr/abl-transduced bone marrow cells succumb to a myeloproliferative disease between 3 and 5 weeks after bone marrow transplantation. The myeloproliferative disease recapitulates many of the hallmarks of human CML and is characterized by high white blood cell counts and extensive extramedullary hematopoiesis in the spleen, liver, bone marrow, and lungs. Use of a retroviral vector coexpressing P210 bcr/abl and green fluorescent protein shows that the vast majority of bcr/abl-expressing cells are myeloid. Analysis of the proviral integration pattern shows that, in some mice, the myeloproliferative disease is clonal. In multiple mice, the CML-like disease has been transplantable, inducing a similar myeloproliferative syndrome within 1 month of transfer to sublethally irradiated syngeneic recipients. The disease in many of these mice has progressed to the development of acute lymphoma/leukemia resembling blast crisis. These results demonstrate that murine CML recapitulates important features of human CML. As such, it should be an excellent model for addressing specific issues relating to the pathogenesis and treatment of this disease.