OBJECTIVE To investigate the effect of diallyl sulfide (DAS) in protection against acute lung injury in rats induced by paraquat(PQ). METHODS A total of 100 male Wistar rats were randomly divided into normal control group,PQ 70 mg·kg-1 model group,and DAS 25,50 and 100 mg·kg-1 treatment groups,with 20 rats in each group. A poisoning model was estalolished after administration ig at a single dose of PQ 70 mg·kg-1,while the normal control group was ip given the same volume of normal saline. DAS 25,50 and 100 mg · kg-1 was intraperitoneally injected 30 min before and after PQ exposure. Five rats in each group were sacrificed at 1,3,6 and 12 h,respectively. The inferior lobe of the right lung was observed by HE staining under an optical microscope. Tissue of the upper lobe of the right lung was used to detect the content of nitric oxide (NO). Alveolar macrophages (AMs) were collected and cultured for 24 h,and the content of nitric oxide synthase(iNOS)in the supernatant was detected. AMs were cultured for 72 h and the expression of iNOS protein in AMs was detected by immunocytochemistry method. RESULTS Compared with normal control group,the alveolar structure of PQ group was severely damaged and the pathological score was significantly increased(P<0.01). The NO content of PQ group was significantly higher than in normal control group(P<0.01). The content and protein expression of iNOS were significantly increased in PQ group(P<0.01). Compared with PQ group,the lung injury score of rats in DAS 50 mg·kg-1 group at 3,6 and 12 h and in the DAS 100 mg·kg-1 group at each time point was decreased(P<0.05). Compared with PQ group,the NO content of DAS 25 and 50 mg · kg-1 group was decreased(P<0.05),and the NO content of DAS 100 mg · kg-1 group was significantly reduced(P<0.01). The content of iNOS was reduced in DAS 100 mg · kg-1 group(P<0.05). Compared with PQ group,the expression of iNOS protein in DAS groups was decreased(P<0.05). CONCLUSION DAS can inhibit the oxidative damage in rats induced by PQ.