AIM: To investigate whether increased intestinal permeability contributes to the pathogenesis and progress of nonalcoholic steatohepatitis by observing its dynamic change in rat models.METHODS: Rat models of nonalcoholic steatohepatitis were established by giving a fat-rich diet. The rats were sacrificed at wk 8, 12 and 16 during the study. Rats fed with normal diet were taken as control. Plasma D-lactate, plasma diamine oxidase, serum lipids and liver transaminases were measured in blood of the femoral artery. Hepatic steatosis and inflammation were assessed by haematoxylin-eosin staining.RESULTS: A rat model of nonalcoholic steatohepatitis was established successfully. Plasma D-lactate level in model group at wk 8, 12 and 16 and diamine oxidase level in model group at wk 12, 16 increased significantly compared with those in control group. There were notable differences of D-lactate and diamine oxidase level in model group between wk 8 and 12 as well as between wk 12 and 16. Serum lipids, liver transaminases and liver injury also increased with disease developmentCONCLUSION: Increased intestinal permeability caused by intestinal bacterial overgrowth and endotoxin-induced intestinal destruction exists in rats with nonalcoholic steatohepatitis, which may partially explain the pathogenesis and progress of this disease.