Summary: To investigate the inducement of cytotoxic T lymphocytes (CTLs) by antigen peptidesmixture from different leukemia cells and the cross-reaction of the mixtures from different celllines, antigen peptides mixtures were prepared from different leukemia cell lines respectively andthen bound with Hsp70 in vitro. Activation and proliferation of PBMC were observed after stimu-lation with different Hsp70-peptide complexes. The ratio of CD8+ in proliferative cells was ana-lyzed by flow cytometry. The cytotoxicity of the activated PBMC to different target cells was as-sayed. The results showed that the antigen peptides from different leukemia cell lines, bound withHsp70, could activate PBMC effectively, and stimulate the activated PBMC to proliferate. Theproliferative PBMC had specific cytotoxicity to corresponding leukemia cells. CD8+ cells, account-ing for a high proportion in proliferative cells, had a specific cytotoxicity to leukemia cells fromwhich antigen peptides were prepared, suggesting that these CD8+ cells were CTLs specific toleukemia cells. CTLs activated by Hut78-peptides or Molt4-peptides had a significantly strongercytotoxicity to Hut78 cells, Molt4 cells and Jurkat cells than that of CTLs activated by HL-60-peptides (P＜0. 05). And the cytotoxicity of CTLs activated by Hut78/Molt4-peptides to Jurkatcells was significantly stronger than that of CTLs activated by either Hut78-peptides or Molt4-peptides alone (P＜0.05). It is concluded that antigen peptides mixtures from leukemia cells caninduce specific antitumor CTLs. There exists cross-reactivity among antigen peptides mixturesfrom different cell lines of the same type leukemia and more cross-reactive antigen peptides couldbe obtained from more cell lines, suggesting that antigen peptides mixture with broad antigenicspectrum could be prepared by using multiple leukemia cell lines.