Abstract: Objective: To investigate the expression of cytokines including IFN- γ , IL- 12 and TNF-αsecreted by PBMCs after stimulation with recombinant Bacille Calmette- Guerin (BCG), and to study the anti- tumor effect of BCG- activated killer cells (BAK). Methods: Recombinant hIFN- α - 2b- BCG,wild- type BCG and wild- type BCG+ hIFN- α - 2b were used to stimulate the peripheral blood mono-cytes (PBMC) in different concentrations in vitro. Supernatant was collected at various time points and IFN- γ , IL- 12 and TNF- αwere detected by an enzyme- linked immunosorbent assay (ELISA). The data from every combination of two groups among the three were contrasted after statistical analysis. Results: Compared with the other groups, recombinant BCG can induce higher density cytokines than wild- type BCG or wild- type BCG+ hIFN- α - 2b (P<0.05). The results of the LDH release assay show that the antitumor activity of BAK cells stimulated by recombinant BCG has the highest cytotoxicity of all of the groups. Conclusions: The expression of IFN- γ , TNF- α , and IL- 12 in PBMCs stimulated by recombinant BCG is higher than those levels in cells stimulated by wild type BCG, suggesting enhanced antitumor activity of BAK when cells are treated with recombinant BCG.