AIM: To investigate the changes of gut microflora and endotoxin levels in rats with acute liver failure (ALF) induced by D-galactosamine (GalN).METHODS: Flora and endotoxin levels in the jejunum, ileum and colon in normal rats (group A) and rats with GalNinduced ALF were determined at 24 h (group B) or 48 h (group C) after GalN injection, as well as the endotoxin level in portal venous blood (PVB) and right ventricle blood (RVB) were determined by chromogenic limulus amoebocyte assay.RESULTS: Intestinal (jejunum, ileum, colon)lactobacillus count was statistically reduced in group B compared with those in group A (3.4±0.3 vs4.9±0.3, 6.1±0.4 vs 8.0±0.3,8.1±0.2 vs 9.3±0.2, P＜0.001, P＜0.001 and P＜0.001respectively) and recovered partially in the group C compared with those in the group B, whereas the count of Enterobacteriaceae in the jejunum, ileum and colon in group B was increased markedly compared with those in the group A (5.1±0.3 vs 3.6±0.2, 6.9±0.5 vs 5.3±0.3,8.7±0.2 vs7.6±0.1, P＜0.001, P＜0.05 and P＜0.05 respectively)and restored partially in the group C compared with those in the group B. The endotoxin level in ileum was increased in the group B compared with those in the group A (111.3±22.8 vs 51.5±8.9, P＜0.05). In addition, the endotoxin level in PVB was obviously increased in group B compared with that in the group A (76.8±9.1 vs40.6±7.3,P＜0.01) and reduced to the baseline at 48 h (group C).CONCLUSIOM: Severely disturbed gut flora in rats with GalN-induced acute liver failure plays an important role in the elevation of endotoxin level in PVB.