B1 kinin receptor (B1R) is up-regulated by endotoxins and thus may represent a therapeutic target in sepsis. We investigated the expression and role of B1R and B2R in the acute phase of lipopolysaccharide (LPS)-induced endotoxin shock in C57BL/6 mice (WT) and B1R and B2R knock out mice (B1KO, B2KO). B1R mRNA was enhanced from 6 to 48 h after LPS while B2R mRNA was further increased in B1KO. Maximal hypotension was found 24 h after LPS, and was more pronounced in B1KO, but was reduced in B2KO. Glomerular filtration rate was more reduced by LPS in B1KO than in WT and B2KO. Glycemia was reduced by LPS and particularly in B1KO and B2KO mice. Mortality was increased by LPS in B1KO. These data suggest that the up-regulated B1R plays, at least transiently, a significant beneficial role in acute LPS-induced hypotension. Conversely, supra activation of B2R could be also involved in the increased mortality observed in B1KO mice.