BACKGROUND A growing body of literature suggests an association between methane and constipation. Studies also link degree of methane production to severity of constipation and have shown constipation is improved following antibiotics. OBJECTIVE We aim to conduct a systematic review and meta-analysis to examine the cumulative evidence regarding the association between methane and constipation. METHODS A literature search was performed using MEDLINE and Embase to identify studies where the presence (or absence) of methane was assessed in constipated subjects. Search terms included "methane," "breath test," "constipation," "motility," "transit," "irritable bowel syndrome" and/or "IBS." Pooled odds ratios were generated using a random effects model. In a separate analysis, studies that measured intestinal transit in methane and non-methane subjects were systematically reviewed. RESULTS Nine studies met inclusion criteria for the meta-analysis. Among these, 1,277 subjects were examined by breath testing (N = 319 methane producers and N = 958 methane non-producers). Pooling all studies, a significant association was found between methane on breath test and constipation (OR = 3.51, CI = 2.00-6.16). Among adults only, methane was significantly associated with constipation (OR = 3.47, CI = 1.84-6.54). Similar results were seen when only examining subjects with IBS (OR = 3.60, CI = 1.61-8.06). The systematic review identified eight additional papers which all demonstrated an association between methane and delayed transit. CONCLUSIONS We demonstrate that methane present on breath testing is significantly associated with constipation in both IBS and functional constipation. These results suggest there may be merit in using breath testing in constipation. Moreover, methane may be used to identify candidates for antibiotic treatment of constipation.