A double-blind, randomized parallel group trial comparison study was performed in 63 patients with irritable bowel syndrome for evaluation of effectiveness and safety of Tiropramide. Over a treatment period of 4 weeks, Tiropramide (300 mgjday) were administered in 32 patients and placebo in 31 patients with irritable howel syndrome. The degrecs of symptom scores for abdominal pain, belching, flatulence, diarrhea, abdominal discomfortnesi, inadequate defecation, borborygmi, etc were assessed every week by interview of pat:ient.s during the treatment. At the end of the four week. treatment, 78.2% of the treatment group with Tiropramide and 40.5% of placebo group were markedly improved their symptoms. The degrees of symptom scores for abdominal pain, inconiplete evacuation, borborygmi, flatulence, abdominal distension, and intensity of nausea showed significant improvement in the treatment group compared with placebo group in each week assessrnent. One patient with Tiropramide treatment and two patients of placebo group experiencecl aggravation of symptoms during treatment but no one had adverse reaction during treatment. These results suggest that Tiropramide is effective and safe for the treatment of irriitable bowel syndrome.