Objective: To evaluate the protective activity of antioxidants, viz. trolox and quercetin, against sulfur mustard (SM)-induced cytotoxicity. Materials and Methods: Cytotoxicity of various concentrations (20-640 μM) of SM, in the presence or absence of 10 μM trolox or quercetin (-0.5, 0, or +0.5 h) was determined in human peripheral blood lymphocytes after 6-h exposure. Cell viability was measured by Trypan blue dye exclusion (TBDE). Further, a cytotoxic concentration of SM (80 μM) was challenged by the two antidotes (-0.5 h) and cell viability was measured by TBDE and leakage of intracellular lactate dehydrogenase (LDH). Mitochondrial integrity and peroxide levels were measured by 3-4,5-dimethyl thiazol-Z-yl)-2,5-diphenyltetrazolium bromide and 2′,7′-dichlorofluoroscin diacetate assay, respectively. Morphological changes of cells exposed to 320 μM SM (with or without antidotes) were also visualized under light microscope. Results: On the basis of TBDE, SM caused cell death of approximately 50% at 80 μM and 100% at 640 μM, respectively. Pretreatment of trolox conferred significant protection compared with quercetin. Also, pretreatment of trolox significantly reduced cell death and LDH leakage caused by 80 μM SM but did not prevent the loss of mitochondrial integrity. Trolox significantly reduced the levels of peroxides generated by SM. The better protection offered by trolox was evidenced in cell morphology studies too. Conclusion: Pretreatment (-0.5 h) of trolox afforded significant protection against SM-induced cytotoxicity in human lymphocytes. The protection was related to the antioxidant property of trolox, a water soluble analog of α-tocopherol.