Enteric microbiota is increasingly being recognized as an important factor in the pathogenesis of irritable bowel syndrome (IBS). The reported prevalence of small intestinal bacterial overgrowth (SIBO) in subjects with IBS is highly variable and there is no consensus on the role of SIBO in different subtypes of IBS, and indications and methods of testing. A comprehensive literature search was performed for studies applying tests for SIBO in subjects with IBS. After applying prospectively decided exclusion criteria, the eligible papers were examined using a meta-analysis approach for the prevalence of SIBO in subjects with IBS using different tests. The odds ratios (OR) of SIBO among subjects with IBS as compared to healthy controls using different tests were calculated. Of the available studies (22, 17, 5, and 3 using lactulose and glucose hydrogen breath tests [LHBT and GHBT], jejunal aspirate culture, and more than one tests, respectively) meeting the inclusion criteria, 36.7% (95% CI 24.2-44.6) had a positive test for SIBO. Patients with IBS were 2.6 (95% CI 1.3-6.9) and 8.3 (95% CI 3.0-5.9) times more likely to have a positive test for SIBO as compared to healthy controls using GHBT and jejunal aspirate culture, respectively. Patients with diarrhea-predominant IBS were more likely to have positive GHBT as compared to the other subtypes. Patients with IBS were more likely to have SIBO as compared to healthy subjects using GHBT and jejunal aspirate culture but not using LHBT. Patients with diarrhea-predominant IBS more often have SIBO. This article is protected by copyright. All rights reserved.