GOALS: The aim of this study was to assess the efficacy and safety of enteric-coated peppermint oil capsules compared with placebo for the treatment of active irritable bowel syndrome (IBS). BACKGROUND: IBS is a common disorder that is often encountered in clinical practice. Medical interventions are limited and the focus is on symptom control. STUDY: Randomized placebo-controlled trials with a minimum treatment duration of 2 weeks were considered for inclusion. Cross-over studies that provided outcome data before the first cross-over were included. A literature search upto February 2013 identified all applicable randomized-controlled trials. Study quality was evaluated using the Cochrane risk of bias tool. Outcomes included global improvement of IBS symptoms, improvement in abdominal pain, and adverse events. Outcomes were analyzed using an intention-to-treat approach. RESULTS: Nine studies that evaluated 726 patients were identified. The risk of bias was low for most of the factors assessed. Peppermint oil was found to be significantly superior to placebo for global improvement of IBS symptoms (5 studies, 392 patients, relative risk 2.23; 95% confidence interval, 1.78-2.81) and improvement in abdominal pain (5 studies, 357 patients, relative risk 2.14; 95% confidence interval, 1.64-2.79). Although peppermint oil patients were significantly more likely to experience an adverse event, such events were mild and transient in nature. The most commonly reported adverse event was heartburn. CONCLUSIONS: Peppermint oil is a safe and effective short-term treatment for IBS. Future studies should assess the long-term efficacy and safety of peppermint oil and its efficacy relative to other IBS treatments including antidepressants and antispasmodic drugs.