The aim was to investigate the cytolytic activity of cytotoxic T lymphocytes (CTL) induced by dendritic cells (DC) derived from human cord blood in vitro. Human cord blood mononuclear cells (CBMNC) were cultured in vitro with addition of various cytokines. DC was confirmed by morphology, immune phenotype and capacity of stimulating MLR (mixed lymphocyte reaction). CTL were generated through the co-culture of autologous T lymphocytes and DC. (51)Cr-release assays were performed for the measurement of cytotoxicity of CTL. The results showed that distribution of the subgroups of T lymphocytes in CBMNC was similar to that in adult peripheral blood. The percentage of CD1a-expressing cells in CBMNC was very low, merely (0.41 +/- 0.09)%. During culture, DC became larger and more irregular in shape. Spiny dendrites or multiple cell processes in morphology emerged on the surface of DC. Among the cell populations at 15 days of culture, there were (28.4 +/- 3.55)% of CD1a-expressing cells, (63.67 +/- 23.33)% of CD86-positive, (8.7 +/- 1.49)% of CD83-positive and (32.5 +/- 1.53)% of HLA-DR-positive cells. DC derived from CBMNC is capable of stimulating the proliferation of allogeneic lymphocytes in MLR. CTL derived from autologous T lymphocytes induced by dendritic cells pulsed with lysates of HL-60 cells, possessed specific cytolytic effects against HL-60 cells. In conclusions, relatively high percentage of CD1a-expressing cells can be generated in culture system of this study. DC derived from cord blood is able to induce the production of anti-leukemic CTL in vitro.