This was an exploratory study of renzapride in 168 male and female patients with non-D, non-C irritable bowel syndrome (IBS). Patients were randomized to placebo or renzapride (1, 2, or 4 mg/day) for 8 weeks. The primary efficacy variable was patient-reported satisfactory relief of IBS symptoms. Secondary variables included relief of abdominal pain/discomfort. The proportion of patients reporting satisfactory relief of their IBS symptoms for at least 50% of the time did not differ significantly from those on placebo. However, post hoc analysis in women showed differences in responder rate on renzapride versus placebo of 18.2% (95% CI −5% to 42%; P = 0.066) during weeks 1–4 and 6% (95% CI −21% to 33%; P = 0.339) during weeks 5–8. Renzapride was well tolerated and most adverse events were mild to moderate in intensity. Further studies are warranted to determine whether renzapride is beneficial in this patient population.