AIM: to evaluate the effectiveness of probiotic therapy for suppressing relapse in patients with inactive ulcerative colitis(UC).METHODS: Bio-Three tablets, each containing 2 mg of lactomin(Streptococcus faecalis T-110), 10 mg of Clostridium butyricum TO-A, and 10 mg of Bacillus mesentericus TO-A, were used as probiotic therapy.Sixty outpatients with UC in remission were randomly assigned to receive 9 Bio-Three tablets/day(BioThree group) or 9 placebo tablets/day(placebo group)for 12 mo in addition to their ongoing medications.Clinical symptoms were evaluated monthly or on the exacerbation of symptoms or need for additional medication. Fecal samples were collected to analyze bacterial DNA at baseline and 3-mo intervals. Terminal restriction fragment length polymorphism and cluster analyses were done to examine bacterial components of the fecal microflora.RESULTS: Forty-six patients, 23 in each group,completed the study, and 14 were excluded. The relapse rates in the Bio-Three and placebo groups were respectively 0.0% vs 17.4% at 3 mo(P = 0.036), 8.7%vs 26.1% at 6 mo(P = 0.119), and 21.7% vs 34.8%(P = 0.326) at 9 mo. At 12 mo, the remission rate was 69.5% in the Bio-Three group and 56.6% in the placebo group(P = 0.248). On cluster analysis of fecal flora, 7 patients belonged to cluster Ⅰ, 32 to cluster Ⅱ,and 7 to cluster Ⅲ.CONCLUSION: Probiotics may be effective formaintaining clinical remission in patients with quiescent UC, especially those who belong to cluster Ⅰ on fecal bacterial analysis. AIM: to evaluate the effectiveness of probiotic therapy for suppressing relapse in patients with inactive ulcerative colitis (UC). METHODS: Bio-Three tablets, each containing 2 mg of lactomin (Streptococcus faecalis T- 110), 10 mg of Clostridium butyricum TO- A and 10 mg of Bacillus mesentericus TO-A, were used as probiotic therapy. Sixty outpatients with UC in remission were randomly assigned to receive 9 Bio-Three tablets / day (BioThree group) or 9 placebo tablets / day for 12 mo in addition to their ongoing medications. Clinical symptoms were required monthly or on the exacerbation of symptoms or need for for supplementary. Fecal samples were collected to analyze bacterial DNA at baseline and 3-mo intervals. Terminal restriction fragment length polymorphism and cluster Analyses were done to examine bacterial components of the fecal microflora .RESULTS: Forty-six patients, 23 in each group, completed the study, and 14 were excluded. The relapse rates in the Bio-Three and place bo groups were respectively 0.0% vs 17.4% at 3 mo (P = 0.036), 8.7% vs 26.1% at 6 months (P = 0.119), and 21.7% vs 34.8% (P = 0.326) at 9 months , the remission rate was 69.5% in the Bio-Three group and 56.6% in the placebo group (P = 0.248). On cluster analysis of fecal flora, 7 patients belonged to cluster I, 32 to cluster II, and 7 to cluster III .CONCLUSION: Probiotics may be effective for maintenance trials remission in patients with quiescent UC, especially those who belong to cluster I on fecal bacterial analysis.