The aim of this study was to determine the effect of exogenous GSH, an important antioxidant containing thiol group, on total antioxidant capacity (TAC) and total oxidant capacity (TOC), adenosine deaminase (ADA), a significant indicator of cellular immunity, and nitric oxide (NO) concentrations in rabbits. Sixteen healthy New Zealand rabbits were divided into 2 groups as control and GSH-treated group. Animals in control group received single intraperitoneal (ip) administration of 0.9% saline. Rabbits in GSH-treated group received reduced L-glutathione (10 mg/kg) (ip). Blood samples were taken from the marginal ear vein 0, 3, 6 and 12 hours after injection. Plasma TAC and NO levels were not statistically different between control and GSH group at 0 and 12 hours. Plasma TAC level was found to be significantly higher (p < 0.05) while NO level was found to be significantly lower (p < 0.05) in GSH treated group when compared to control group at 3 and 6 hours. Plasma TOC and ADA activity were not statistically different between control and GSH group during experiment. In conclusion, exogenous GSH resulted in an alteration of TAC and NO but not TOC and ADA, so exogenous GSH may be a valuable enhancer of the antioxidant system.