BACKGROUND: Tumor necrosis factor(TNF) has been considered as an important candidate for cancer gene therapy based on its potent anti-tumor activity. The mechanisms of TNF cytotoxicity are not clearly understood and some has reported that reactive oxygen species(ROS) might be associated with them, but there is controversy about antioxidant effect on TNF cytotoxicity. This study was designed to compare the TNF cytotoxicity after antioxidant pretreatment with that of control to evaluate the role of ROS in the mechanism of TNF cytotoxicity. METHOD: We compared the TNF cytotoxicies to WEHI164(murine fibrosarcoma cell line) and ME180(human cervix cancer cell line) after antioxidant pretreatment with those of control by MTT(dimethylthiazolyl-diphenyltetrazolium bromide) assay. RESULTS: In the control group, the TNF cytotoxicities were 92.2+/-2.8%(WEHI164) and 59.9+/-7.0%(ME180). In the TMTU(tetramethyl thiourea) pretreatment group, those were 91.4+/-3.7% and 74.6+/-7.0%. In the PMZ(promethazine) pretreatment group, those were 90.2+/-2.5% and 62.5+/-5.7%. In the BHT(butylated hydroxytoluene) pretreatment group, those were 93.2+/-1.3% and 66.3+/-6.1%. So there was no reduction in TNF cytotoxicity after antioxidants pretreatment. CONCLUSION: The ROS may not have major role in the mechanisms of TNF cytotoxicity.