Sulphur mustard [bis(2-chloro ethyl) sulfide] (SM), a bifunctional alkylating agent has been frequently used as a chemical warfare agent. In the present study, the effects of sodium 2-3-dimercaptopropane sulphonic acid (DMPS) on some biochemical and histological parameters in mice, exposed to 1/4LC50 concentration of SM vapor (10.5 mg/m3) were examined over a period of seven days. Exposure of SM resulted in a significant loss of blood, hepatic and pulmonary glutathione (GSH) and an elevation of hepatic and pulmonary oxidized glutathione (GSSG). These biochemical changes were accompanied by a number of histopathological alterations. The most prominent was congestion and degeneration in viscera and obliteration of chromatin material. These biochemical and histopathological changes were less marked in animals pre-administered with DMPS followed by DMPS exposure indicating some protective value of the thiol (DMPS) against SM induced oxidative injury in mice.