This study is designed to investigate the effects of an oral probiotic (VSL#3; a mixture of "healthy" bacteria for the intestines) compared to an antibiotic or placebo in preventing infection developing in the abdominal fluid ("ascites") that collects in patients with advanced liver disease ("cirrhosis"). Patients already having had infection will be excluded from the study. Clear inclusion and exclusion criteria will be met and patients will be monitored throughout the study to examine whether they have required more hospitalisations, their rate infection in abdominal fluid or elsewhere and the level of liver function.