Purpose: As basic information of antioxidant treatments for the patient with paraquat intoxication, in human peripheral lymphocytes, the cytotoxicity of paraquat was measured, and to evaluate the antioxidant effect of vitamin C and deferoxamine against this cytotoxicity, malondialdehyde (MDA), superoxide dismutase (SOD) activity and total antioxidant status (TAS) were measured. Methods: From 10 healthy adults, after obtaining a consent, 20ml peripheral blood was collected. Experimental groups were divided to (1) control group, the group treated with an identical amount of saline, (2) P group: the group treated with paraquat only, (3) PV group: the group treated with paraquat followed by vitamin C 30 minutes later, (4) PD group: the group treated with paraquat followed by deferoxamine 30 minutes later, (5) PVD group: the group treated with paraquat followed by vitamin C 30 minutes later and subsequently deferoxamine one hour later, and (6) PDV group: the group treated with paraquat followed by deferoxamine 30 minutes later and subsequently vitamin C 1 hour later, and thus to total 6 groups. In each group, 10 samples of peripheral blood was assigned and $100{mu}M;paraquat,;100{mu}M$ vitamin C, and $100{mu}M$ deferoxamine were used as reagent. Lymphocytes were isolated, cultured, and cytotoxicity was measured by the Microculture Tetrazolium method (MTT assay), MDA and SOD activity, and TAS concentration were measured. Results: In regard to the cytotoxicity measured in each group, their cytotoxicity was decreased in the group treated with antioxidants, in comparison with the group treated with paraquat only. In the cases that the order of the treatment of these two antioxidants was altered, viability in the PDV group $(1.077{pm}0.121)$ was increased more that the PVD group $(0.888{pm}0.152)$ statistically significantly (p=0.018). Concerning the amount of MDA, in comparison with the P group $(6.78{pm}0.93{mu}mol/L)$, after the treatment of each antioxidant, the concentration of MDA was decreased statistically significantly (p<0.05). In the group treated with two antioxidants together, in comparison with the group treated only with one antioxidant, the amount of MDA was increased statistically significantly $(PV:;3.96{pm}0.98{mu}mol/L,;PD:;4.92{pm}1.50{mu}mol/L,;PVD:;3.22{pm}0.83{mu}mol/L,;and;PDV:;3.42{pm}0.95{mu}mol/L,;p=0.007)$. The concentration of SOD measured in the blood in each group after the administration of paraquat, in comparison with the control group, a pattern of the elevation of SOD activity and subsequent decrease was detected, however, it was not statistically significant. In the comparison of the groups treated with antioxidants, in comparison with the P group $(1419.9{pm}265.9{mu}mol/L)$, SOD activity was decreased statistically significantly in only the PDV group $(1176.4{pm}238.9{mu}mol/L)$ (p=0.017). In regard to TAS measured in each group, in comparison with the P group $(0.87{pm}0.05{mu}mol/L)$, in all groups treated with the antioxidants, the PV group was $1.00{pm}0.03{mu}mol/L$ (p=0.005), the PD group was $9.01{pm}0.24{mu}mol/L$ was $4.64{pm}3.98{mu}mol/L$ (P=0.005), and the PDV group was $9.41{pm}0.27{mu}mol/La$ (p=0.005), and thus total antioxidant activity was increased statistically significantly In a multiple comparison test, the PDV group showed the highest total antioxidant activity (p<0.0001). Conclusion: The result of the assessment of the antioxidant effect of vitamin C and deferoxamine on paraquat-induced cytotoxicity showed that in regard to cytotoxicity, SOD activity and TAS measurement, the best result was observed in the PDV group. Therefore, it was found that vitamin C and deferoxamine were effective antioxidants for the paraquat-induced cytotoxicity, and it suggests that the administration of deferox..