 Intestinal translocation of Gram-negative bacteria occurs in patients with advanced cirrhosis. Long-term oral administration of 400 mgday of norfloxacin a fluoroquinolone antibiotic is known to induce selective intestinal decontamination against Gram-negative bacteria. A randomized, double-blind, placebo-controlled trial of oral norfloxacin 400 mgday for 1 year has been conducted in a small series of patients with advanced cirrhosis and low ascitic fluid protein concentrations 1.5 gdL. This trial showed that norfloxacin therapy significantly increased the 1-year probability of being free of a first episode of spontaneous bacterial peritonitis SBP and improved 3-month survival. In this previous study, oral norfloxacin therapy was also found to decrease the risk of development of hepatorenal syndrome, a very severe complication of cirrhosis. It has been suggested that bacterial translocation, through the release of bacterial byproducts, results in systemic inflammation and subsequent systemic vasodilation which precipitates hepatorenal syndrome. Since systemic vasodilation plays a role in the development of ascites, bacterial byproducts via circulatory alterations may contribute to mechanisms leading to ascites formation. It is important to note that a randomized, double-blind, placebo-controlled trial of oral administration of the quinolone ciprofloxacin 500 mgday for 1 year has been conducted in a small series of patients with moderately severe cirrhosis, low ascitic fluid protein concentrations 1.5 gdL and no prior history of SBP. However, ciprofloxacin therapy did not significantly increase the 1-year probability of being free of SBP. Taken together the findings of these 2 previous small-size trials suggest that long-term oral quinolone therapy is effective mainly in patients with severe cirrhosis. This is why we decided to perform a large multicenter, randomized, parallel, placebo-controlled trial assessing the effects of norfloxacin on survival in patients with cirrhosis and severe liver failure Child-Pugh grade C. In addition, the effects of norfloxacin on the development of main complications of cirrhosis will be investigated. 