Objective: To investigate the effects of interferon-a (IFN-a ) and IFN-a combined with interleukin-6 (IL-6) on growth and expression of bcr-abl, bcl-2 and c-myc genes in the mononuclear cells (MNCs) from bone marrow (BM) of patients with chronic myelogenous leukemia (CML). Methods: MNCs were collected from BM of the patients with CML in chronic phase by centrifugation in lymphocyte separation medium and cultured in liquid with IFN-a (200U/ml) or IFN-a (200U/ml) plus IL-6 (100 ng/ml). The growing cells were counted every day. The expression levels of b -actin, bcr-abl, bcl-2 and c-myc genes in the MNCs incubated for 24 h were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and relatively quantitative analysis of the amplified fragments by optical density scanning for the bands on gel. Results: The cell growth was markedly suppressed by IFN-a but the degree of cell-growth inhibition was slightly decreased by IL-6 on the basis of IFN-a effect. The expression of bcr-abl chimeric gene was intensely inhibited by IFN-a or IFN-a plus IL-6. The expression of bcl-2 gene was suppressed by either IFN-a or IFN-a plus IL-6, whereas that of c-myc gene was also inhibited by IFN-a but strongly elevated by IL-6 on the basis of IFN-a action. Conclusions: Both IFN-a and IFN-a plus IL-6 can inhibit the expression of anti-apoptosis gene such as bcr-abl and bcl-2 and regulate the expression of the gene related to cell proliferation and differentiation such as c-myc. Either IFN-a or IFN-a combined with IL-6 will serve as a trustful strategy of clinical treatment for CML.