Methods: A prospective, double blind, randomized controlled trial was conducted in consecutive high-risk cirrhotic patients with ascites who had either recovered from an episode of SBP (secondary prophylaxis) or who never had SBP but were at high risk for development of SBP (low ascitic fluid protein or serum bilirubin ≥2.5 mg/dL; primary prophylaxis). Norfloxacin 400 mg once daily with synbiotic capsules (Streptococcus faecalis JPC 30 million, Clostridium butyricum 2 million, Bacillus mesentericus JPC 1 million, Lactobacillus sporogenes 50 million spores) 2 t.i.d. (group I) or norfloxacin 400 mg once daily with placebo (group II) was given and occurrence of SBP within a period of 6 months (primary endpoint) or side-effects of therapy and mortality (secondary endpoints) were recorded. Every patient received IV albumin to maintain a serum albumin level of >3.2 g/dl. SBP was treated with intravenous antibiotics with albumin.