Four patients affected by chronic myeloid leukemia who developed osteolytic lesions in the course of the disease are described. According to the literature, the appearance of these alterations seems to signify an unfavorable prognosis, since they occur slightly before or even at the same time as the blastic transformation of the disease. However, in one case bone biopsy showed a metastasis of a solid tumor, emphasizing the importance of this procedure in order to give a more precise clinical evaluation, both diagnostic and therapeutic.