Chronic myeloid leukemia (CML) is a hematological malignancy resulting from clonal expansion and massive accumulation of leukemic myeloid cells that retain differentiation and maturation capacity. Since CML cell accumulation has been related to apoptosis inhibition by the product of the BCR-ABL gene, attempts to eradicate leukemic cells would require therapeutic drugs able to overcome this inherent resistance. Here, we investigated in vitro the apoptotic effect of all-trans retinoic acid (ATRA) and cytosine arabinoside (ARA-C), employed alone, in combination or in sequence, on freshly isolated cells from 10 patients with chronic-phase CML. Our cell cultures showed that both ATRA and ARA-C were able to induce apoptosis in CML cells, even if ARA-C resulted more effective than ATRA. The combined use of ATRA and ARA-C seemed to have only an additive effect while the sequential use did not show any advantage. These in vitro observations indicate that ATRA and ARA-C may be effective in reducing CML cells through apoptosis induction, suggesting that it could be worthwhile to examine ATRA and ARA-C combinations in the therapy of CML.