AIM: To estimate the prevalence of small intestinal bacterial overgrowth (SIBO) in our geographical area (West Sicily, Italy) by means of an observational study, and to gather information on the use of locally active, nonabsorbable antibiotics for treatment of SIBO. METHODS: Our survey included 115 patients fulfilling the Rome Ⅱ criteria for diagnosis of irritable bowel syndrome (IBS); a total of 97 patients accepted to perform a breath test with lactulose (BTLact), and those who had a positive test, received Rifaximin (Normix., Alfa Wassermann) 1200 mg/d for 7 d; 3 wk after the end of treatment, the BTLact was repeated. RESULTS: Based on the BTLact results, SIBO was present in about 56% of IBS patients, and it was responsible for some IBSrelated symptoms, such as abdominal bloating and discomfort, and diarrhoea. 1wktreatment with Rifaximin ted the BTLact to negative in about 50% of patients and significantly reduced the symptoms, especially in those patients with an altated constipation/diarrhoeavariant IBS.CONCLUSION: SIBO should be always suspected in patients with IBS, and a differential diagnosis is done by means of abreath test. Rifaximin may represent a valid approach to the treatment of SIBO.