Accumulating evidence suggests that deterioration of the gut flora contributes to the pathogenesis of alcoholic liver cirrhosis (ALC). However, the ALC flora profile and its response to probiotic treatment have not been fully examined. This double-blind placebo-controlled study aimed to evaluate whether the probiotic beverage Yakult 400 (Y400), which contains Lactobacillus casei strain Shirota, improves liver function in ALC patients, and to analyze the precise gut flora profile by real-time quantitative PCR (qPCR).