Bacterial intestinal overgrowth syndrome (SIBO) treatment is based on antibiotics. Probiotics have been shown to give similar results, whilst no study is available about prebiotics. This study evaluated the addition of probiotics or prebiotics to antibiotics on SIBO symptoms in a 6-month follow-up. We enrolled 40 patients (14 males and 26 females) reporting abdominal compliant without gastrointestinal diseases/alarm symptoms. SIBO was diagnosed by the agreement of lactulose and glucose breath tests. Patients were randomly divided into two groups homogeneous for sex and age: group 1 received Rifaximin 400 mg/day for 7 days/month followed by Lactobacillus casei for 7 days more and group 2 antibiotic followed by short chain fructo-oligosaccharides. All patients recorded a questionnaire for subjective symptom evaluation according to Rome III criteria and Bristol scale for stool characters before the study and after 6 months. Statistics: Student's t and Fisher's exact tests. In group 1, a significant improvement was obtained in 5 out of 6 symptoms, whilst in group 2 in 4 out of 6 symptoms (nausea and number of bowel movements failed to improve). Despite we observed a trend of probiotics to be more effective than prebiotics, the difference in the percentage of improved symptoms was not significant (83,3% vs 66.6%; p= 0.57). Our preliminary data show a good outcome with sequential antibiotic-probiotic/prebiotic administration in patients with SIBO.