Oxidative stress during inflammation can increase inflammation and damage tissue. Nigella sativa L. (NS) showed many pharmacological properties including antioxidant and anti-inflammatory activities.In this study, the preventive effect of NS on lung inflammation and oxidative stress induced by lipopolysaccharide (LPS) in the rats was investigated.Male rats were assigned to: Control, LPS (1 mg/kg, i.p.), LPS + NS (100, 200, 400 mg/kg, i.p.), (10 per group). Saline (1 ml/kg) was intra-peritoneal (i.p.) injected instead of LPS in the rats of the control group. LPS dissolved in saline and injected i.p. daily for 14 days. Treatment with NS extracts started two days before LPS administration and treatment continued during LPS administration. White blood cells (WBC), total and differential as well as oxidative stress index in bronchoalveolar fluid (BALF) and serum, TGF-β1, IFN-γ, PGE, and IL-4 levels in the BALF and lung histopathology were examined.LPS administration increased total WBC, eosinophils, neutrophils, basophils, and monocytes counts as well as oxidative stress markers in the BALF and serum as well as TGF-β1, IFN-γ, PGE, IL-4 levels in the BALF and pathological changes of the lung tissue. All of these effects were reduced by NS extract treatment dose-dependently.These results suggested the protective effects of NS extract on lung inflammation and oxidative stress as well as its effect on lung pathology induced by LPS dose-dependently.