No human myeloid leukemia-derived cell lines possess the ability to acquire a osteoclstic cell phenotype. In contrast, the CD34+ human acute myeloid leukemia cell line MUTZ-3 responds to macrophage-colony-stimulating-factor (M-CSF), receptor activator NF-kB ligand (RANK-L) and tumor necrosis factor-a (TNF-a), cytokines known to be pivotal both in vivo and in vitro for osteoclasts generation from monocytes and CD34+ stem cells. In all respects, MUTZ-3 cells behave as the immortalized equivalent of CD34+ osteoclasts precursors. Upon stimulation with specific cytokine cocktails, they formed numerous multinucleated osteoclasts expressing tartrate resistent acid phosphatase (TRAP) and calcitonin receptors (CTR) within 12 days of culture. MUTZ-3-osteoclasts formed extensive lacunae mineral resorption when cultured on mineralized surface after 21 day of cultures. These findings demonstrate the unique suitability of MUTZ-3 cells as an unlimited source of human CD34+ osteoclasts progenitors for the study of cytokine-induced osteoclast differentiation.