BACKGROUND & AIMS: Pinaverium bromide (pinaverium) is an antispasmodic commonly used to treat irritable bowel syndrome (IBS), but there has been no convincing evidence for its effectiveness and safety. We evaluated these in a prospective, double-blind, placebo-controlled trial. METHODS: Patients with IBS, based on Rome III criteria, were assigned randomly to groups given pinaverium (50 mg, 3 times/day; n = 218) or placebo (3 times/day; n = 209) at 4 hospitals in China, from August 2012 through December 2013. The primary end points were reductions in abdominal pain and Bristol stool score. Secondary end points were reductions in pain and stool frequencies and abdominal discomfort and its frequency. We also evaluated changes in IBS global symptom scores and the number of adverse effects. RESULTS: Based on an intention-to-treat analysis, a significantly larger proportion of patients receiving pinaverium met either of the primary end points (50.0% met an end point at week 2, and 77.5% met an end point at week 4), compared with placebo (P <.001). Pinaverium reduced at least 1 secondary end point in significantly more patients receiving pinaverium (76.1% had a reduction at week 2, and 91.7% had a reduction at week 4) than placebo (P <.001). Based on symptom scores, significantly higher percentages of patients receiving pinaverium believed that their IBS symptoms improved (60%) than in the placebo group (34%; P <.001); 29% of patients in the pinaverium group believed that their IBS symptoms stayed the same (29%) and 11% said they worsened. Pinaverium was not associated with severe adverse effects; common side effects included nausea (3.7%), dizziness (3.2%), increased blood pressure (2.3%), and abdominal discomfort (2.3%). CONCLUSIONS: Based on a controlled trial, pinaverium reduces symptoms of IBS. It can be considered a firstline treatment for IBS. Trial registration: NCT01641224 (www.ClinicalTrials.gov).