The aims of this study were to analyze the composition of umbilical cord blood cells (UCBC), to examine the characteristics of dendritic cells (DC) before and after culture, to search the method of differentiation and increase of DC in vitro and to appraise surface antigen from UCBC. Twelve units of umbilical cord blood were collected from May 2002 to September 2002. Peripheral blood mononuclear cells of 9 cases were collected from healthy adult donors. The nature of UCBC was freshly determined and then UCBC were cultured for 1, 2, 3 and 4 weeks with granulocyte-monocyte colony-stimulating factor (GM-CSF), interleukin 3 (IL-3), recombinant human stem cell factor (SCF) and EPO. Method of flow cytometry was used to determine the number of DC and cell surface antigens before and after culture by using monoclonal antibodies. The monoclonal antibodies included CD4, CD8, CD19, CD34, CD38, CD83, CD1a, CD11c and CDw123. The results showed that amounts of CD34+ progenitors in peripheral blood cells were 0.02 x 10(5)/ml, and amounts of CD34+ progenitors in human UCBC were 0.22 x 10(5)/ml. UCBC cultured for 1, 2, 3 and 4 weeks with GM-CSF, IL-3, EPO and SCF were shown to differentiate into CD1a+ CD11c+ CD83+ CDw123+ DC. Numbers of DC from UCBC remarkably generated in 2-4 weeks and then decreased in number. By culture with cytokines DC increased up to (10.6 - 28.2) x 10(5)/ml in actual numbers. It is concluded that the mononuclear cells of UCB are able to differentiate into CD1a+, CD83+, CD11c+ and CDw123+ DC when UCBC are cultured with proper cytokines of GM-CSF, SCF, EPO and IL-3 for 2-4 weeks. These DCs as antigen presenting cells are possibly effective in cancer immunotherapy.