AIM: To characterize the bifidobacterial microbiota of the colonic mucosa in patients with colon cancer,inflammatory bowel disease or diverticulitis.METHODS: A sample of the distal colonic mucosa was taken during surgery from a total of 34 patients,twenty-one with diagnosed colorectal cancer, nine with diverticulitis and four with inflammatory bowel disease, requiring surgery for their condition. Bacterial DNA was extracted from the resected mucosal samples and bifidobacterial mucosa-associated microbiota was qualitatively and quantitatively determined by means of qualitative and quantitative PCR.RESULTS: Bifidobacteria were found in 100% of the samples from patients with diverticulitis or IBD and a 76% of those suffering colon cancer. The species B. longum and B. bifidum were the most widely found, followed by B. animalis, B. catenulatum and B.adolescentis. B. breve, B. dentium and B. angulatum were not detected in any sample. A significantly higher occurrence of B. longum was observed in patients with diverticulitis than in those with colon cancer or IBD (100%, 62% and 75%, respectively, P ＜ 0.05).Similar results were obtained for B. animalis (56%, 0%and 25%, P ＜ 0.05), while B. adolescentis was only found in the mucosa from patients with colon cancer (5 out of 21, 24%). At the quantitative level, patients with colon cancer or IBD showed lower counts of total Bifidobacterium (4.94 and 5.91 vs 6.96 log Cells/sample,respectively, P ＜ 0.05) and of the species B.longum (4.05 and 4.79 vs 6.76, P ＜ 0.05) than those with diverticulitis.CONCLUSION: Aberrancies in mucosa associated microbiota are present in different intestinal diseases.This may indicate a role of the microbiota in the pathogenesis of these diseases.