Diagnosis of chronic myelogenous leukemia (CML) and non-Hodgkins lymphoma (NHL) have rarely been made simultaneously in the same patient. We report a rare case of a patient with CML-chronic phase who developed a concurrent Philadelphia (Ph)-negative diffuse large B-cell lymphoma. At the time of diagnosis, cytogenetic analysis of peripheral blood and bone marrow cells revealed the Ph-chromosome translocation in all examined metaphases. A lymph node biopsy showed features of diffuse large B-cell lymphoma, and fluorescence in situ hybridization (FISH) of lymph node tissue for BCR-ABL was negative. The patient was treated with R-CHOP (rituximab, cyclophosphamide, vincristine, adriamycin and prednisone) and imatinib mesylate.