The effects of prokinetic treatment with cisapride in patients with constipation-predominant irritable bowel syndrome (IBS) were evaluated in a randomized, doublelind, placebo-controlled study. Sixty-nine IBS patients were assigned to a 12-week treatment with either 5 mg cisapride or placebo t.i.d.; this dosage could be changed of necessary. The mean weekly number of days on which stool was passed in the cisapride and placebo group ncreased to 5.3 and 4.4 (p < 0.05) during weeks 8–12 of reatment, and the number of days with stools of normal consistency increased to 3.5 and 1.9 (p < 0.05), respectively. At week 12, the reduction in severity and frequency scores for abdominal pain was significantly reater (p ≤ 0.05) in the cisapride group (60 and 61%) than in the placebo group (40 and 32%), as it was for abdominal listension (p < 0.05). Cisapride tended to be better than placebo in diminishing flatulence. In 71% versus 39% of he patients the overall rating for the response to treatment was good or excellent at week 12. Cisapride was well tolerated. These results suggest that the drug will be useful for the management of constipation-predominant BS.