Objective To explore the effect on immunological roles of peritoneal macrophages caused by murine hepatoma cells with different metastatic ability. Methods Peritoneal macrophages were isolated from mice bearing with different metastatic ascites hepatoma cells. The levels of nitric oxide(NO) and tumor necrosis factorα(TNF-α) from macrophages stimulated with lipopolysaccharide(LPS) and interferon-γ(IFN-γ) were analyzed, and the cytotoxicity activity of the macrophages was evaluated. In addition, expressions of TFN-γ and transforming growth factorbetal(TGF-β1) were measured by sandwich ELISA in the ascites of mice bearing tumors. Then, antiTGF-β1 antibody was added to the coculture, and its effect on the expression of NO and cytotoxic ability of peritoneal macrophages examined. Results Compared with those from normal mice, the macrophages from mice bearing ascites hepatoma produced significantly less NO and TNF-α when they were activated with LPS and IFN-γ, and the cytotoxic ability also decreased. Both NO expression and the cytotoxic ability of the macrophages from mice with higher mestastic hepatoma were less than those from mice with lower metastasitic hepatoma, but the level of TNF-α of the former was higher. Moreover, abundant IFN-γ and TGF-β1 were detected in the ascites. Although there was no obvious difference in the production of IFN-γ between mice with different hepatomas, the level of TGF-β1 was much higher in the mice with higher metastasitic hepatoma. Finally, the blocking wit