This study conducted a systematic review to assess the quality of existing literature on psychological treatments for irritable bowel syndrome and to quantify the evidence for their efficacy. Three independent reviewers (2 from England, 1 from the United States) coded the quality of 32 studies, 17 of which provided data suitable for meta-analysis. Meta-analysis of efficacy data (50% reduction of symptoms) gave an odds ratio of 12 (95% confidence interval = 5.56-25.96) and a number needed to treat of 2. Psychological treatments are, as a class of interventions, effective in reducing symptoms compared with a pooled group of control conditions. Questions regarding the relative superiority of specific psychological treatments and influence of active versus nonspecific treatment effects remain unanswered.