Blasts from patients with acute myeloid leukemia (AML) can be differentiated in dendritic cells (DCs) using appropriate combinations of cytokines. However, generation of autologous antileukemic cytotoxic T cells using leukemic DCs remains difficult. We have previously reported that expression of costimulatory molecules in cultured AML cells could be induced by gamma-irradiation. In the present study, blasts from 21 patients with AML were cultured in vitro for 2 days, then cells were gamma-irradiated and antigen-presenting cell (APC) characteristics were assessed. gamma-Irradiation induced expression of several characteristics of APCs in AML blasts, including expression of CD80, CD86, and BDCA-4, and were stimulators of allogeneic mixed lymphocyte reactions. Autologous antileukemic cytotoxicity was induced in seven out of ten cases. This study shows that cells with APC characteristics and able to induce ex vivo stimulation of autologous antileukemic T cells can be generated from AML cells using the simple and rapid method of gamma-irradiation of cultured leukemic cells.