Spontaneous bacterial peritonitis (SEP) is one of the most important complication in cirrhotic patients with ascites, but is pathogenesis is not well known, It is thought that the impaired host defences and the passage of enteric bacteria into the mesenteric lymph nodes, named bacterial translocation, may be two important mechanisms in the pathogenesis of SEP. We have studied this phenomenon in an experimental model with oral CC14 induced cirrhotic rats. SEP ocurred in 36% of ascitic rats, all cases being produced by enteric Gram (-) bacteria, Bacterial translocation was observed in 100% of rats with SEP but in 53% of rats without SEP (p<0.05). In all cases the same organism was isolated in ascitic fluid and in mesenteric lymph nodes. These results suggest that bacterial translocation could play an important role in the pathogenesis of SEP.