Dendritic cells (DCs) are known to be generated from leukemic clone from patients with acute and chronic leukemia when cultured in the presence of combination of granulocyte-macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor-alpha (TNF-alpha) and interleukin-4. However, there have been few reports that showed DCs could be effectively differentiated from human leukemia cell lines. In this study, we have shown that a human monoblastic cell line, UG3, was inducible to differentiate into DCs in the presence of GM-CSF and TNF-alpha along monocyte-macrophage lineage. These DCs, consistently displayed dendritic morphology, phenotypes and allogeneic T-cell stimulating capacity. UG3 cells thus may represent a suitable model to further elucidate characteristics of DC differentiation.