Current therapies of chronic myeloid leukemia (CML) do not prevent the progression of the disease towards blastic metamorphosis, and have not resulted in a remarkable prolongation of survival. Splenectomy was proposed with the aim of removing a part of the tumor without cytotoxics and of removing a potentially privileged pool of malignant blast cells. Acute leukemia-like chemotherapy was proposed with the aim of eradicating or better controlling the highly malignant subclones that emerge during the chronic phase. A preliminary analysis of 2 clinical trials these therapeutic measures, suggests that splenectomy does not modify the rate of blastic transformation, during the first 2 to 3 years from diagnosis. Also the rate of blastic transformation is similar for patients receiving hydroxyurea at first, and arabinosyl cytosine (ARA-C), vincristine (VCR) and prednisone (P) thereafter, as for patients receiving from the clinical onset of CML a more intensive chemotherapy with ARA-C, thioguanine (TG) and daunomycin (DAUNO), but not VCR + P.