The interest in the use of human dendritic cells in cancer immunotherapy calls for efficient ex vivo methods of dendritic cell education. To extend the range of methods available, we generated phenotypically characteristic dendritic cells from peripheral blood monocytes incubated with granulocyte-macrophage colony-stimulating factor and interleukin-4 and infected them with an adenovirus containing a humanized version of green fluorescent protein as a marker of gene expression. The levels of expressed protein were high, but they were further increased in combination with cationic liposomes. In comparison to transfection efficiency of the homologous expression plasmid, adenovirus-mediated gene transfer was substantially more efficient. With the aid of liposome-mediated infection, gene transfer into CD83+ dendritic cells was highly effective, resulting in more than 90% of the cells expressing the transgene.