The present study investigated the acute pulmonary toxic effects MgO nanoparticle in rats following their exposure through intratracheal instillation, and investigated the oxidative stress and anti-oxidant status in rats following exposure and also to compare these toxic effects with those of quartz particles.Intratracheal instillation method was used to exposure the nanomaterials to the rats and evaluated for various tissue damage markers like alkaline phosphatase (ALP), lactate dehydrogenase (LDH) in bronchoalveolar lavage (BAL) fluid at 1, 7, 30 days of post exposure intervals. Exposure of nanomaterials caused the dose dependant increase in ALP, LDH activity in BAL fluids of rat lungs indicated the pulmonary toxicity of these nanoparticles, which was supported by the histopathological examinations. Exposure of nanoparticles to rats produced a dose dependant decrease in the levels of TAS, Catalase SOD indicating the induction of oxidative stress.