The prevalence of cirrhosis is increasing in the UK. Decompensation heralds a poor outcome, with mortality in those developing ascites approximately 50% over the following 1-2 years. Spontaneous bacterial peritonitis (SBP) in ascitic fluid further reduces survival and occurs due to a combination of increased intestinal epithelial dysfunction, bacterial translocation to mesenteric lymph nodes and ascitic fluid, and reduced opsonisation and neutrophil function. Even with antibiotic treatment, 3-month mortality from SBP is approximately 40% and results in expensive in-patient care. Several studies have confirmed the benefit of secondary prophylaxis with long-term oral antibiotics in patients with advanced liver disease (e.g. norfloxacin, co-trimoxazole) and others suggest that in patients at high risk of developing SBP, primary antibiotic prophylaxis improves rates of sepsis and survival. Problems with these strategies include emergence of bacterial resistance, and development of antibiotic-associated diarrhoea (including C. difficile infection, which has a high case-fatality rate in those with cirrhosis). Local bacterial resistance profiles and association with C. difficile infection favour the choice of co-trimoxazole in our study population. Patients with advanced cirrhosis taking co-trimoxazole have previously demonstrated reduced liver-related outcomes such as infection and death3. Probiotic preparations alter intestinal bacterial flora and improve intestinal barrier and neutrophil function. Faecal bacterial counts of E. coli and Streptococcus (organisms commonly responsible for SBP) showed a 2-log fall with probiotics, although whether they could reduce the incidence of SBP remains unexamined.