<p><b>OBJECTIVE</b>To investigate the expression of nuclear factor kappa B (NF-kgr;B) and tumor necrosis factor α (TNF-α) in lungtissue of acute paraquat poisoned rats.</p><p><b>METHODS</b>68 maleWistar rats were randomly divided into 2 groups the control group (n = 8), the intoxication group (n = 60). On the 1st, the 3rd, the 7th, the 14th and the 28th day after intoxication, the expression of NF-κB p65 and TNF-α in lungtissue were detected by LSAB immunohistochemistry (IH) staining. Meanwhile, the level of malondialdehyde (MDA) in plasma, and lung homogenate, the content of malondialdehyde (HPY) in lung homogenate were detected.</p><p><b>RESULTS</b>The levels of MDA in plasma on the 1st, the 3rd, the 7th day and in lung homogenate on the 1st, the 3rd day of the intoxication group [in plasma (10.15 ± 3.15), (6.97 ± 1.65) and (5.44 ± 0.66) nmol/ml; in lung homogenate (10.20 ± 2.43), (10.71 ± 171) nmol/ml] were significantly higher than that of the control group [in plasma (3.84 ± 1.04) nmol/ml, in lung homogenate (7.66 ± 0.66) nmol/ml]. The content of HPY in lung homogenate on the 14th and the 28th day after intoxication [(19.98 ± 2.86), (26.06 ± 4.06) µg/0.1 g lung homogenate] were higher than that of the control group [(8.80 ± 1.26) µg/0.1 g lung homogenate] significantly. The expression of NF-κB p65 and TNF-α in lungtissue were both significantly increased on the first day and the 3rd day of the intoxication group compared with the control group and weakened obviously after the 7th day.</p><p><b>CONCLUSION</b>Acute paraquatpoisoning can induce increased expression of both NF-κB p65 and TNF-α in lungtissue; the enhanced activity of NF-κB may take part in the process of pulmonary injury in PQ poisoning.</p>