This study was to investigate the differences of inflammatory reaction and oxidative stress due to sulfur mustard (SM)-induced acute pulmonary injury via two ways in rats. In intraperitoneal and tracheal SM groups, injected intraperitoneally and instilled intratracheally with 0.1 mL diluted SM (0.96 LD 50 = 8 mg/kg) and SM (0.98 LD 50 = 2 mg/kg) were administered in rats. In bronchoalveolar lavage fluid, serum, and alveolar septum, lactate dehydrogenase, glutathione peroxidase, tumor necrosis factor-α, interleukin-1β, interleukin-6, C-reactive protein, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, l -selectin, r-glutamyl transpeptidase, thiobarbituric acid reactive substances levels as well as the expression of CD4, CD20, CD68, 8-hydroxy deoxyguanosine, nuclear factor-E2-related factor 2, and heme oxygenase-1 measured by ELISA, immune scatter turbidimetry and immunohistochemical method in the intraperitoneal SM group were increased at each time-point compared with the tracheal SM groups, respectively. These data demonstrated an increased inflammatory reaction and oxidative stress indices in rat via intraperitoneal injection under similar SM LD 50 doses. [ABSTRACT FROM AUTHOR]