OBJECTIVE Bacterial gastroenteritis seems to be a risk factor of irritable bowel syndrome (IBS). The incidence of post-infectious IBS (PI-IBS) was reported to be in the range of 7-31%, but few studies have reported long term follow-up results. So, we investigated the clinical course and prognosis of PI-IBS three years after shigella infection. METHODS The subjects were recruited from our previous study, in which we investigated the incidence and risk factors of PI-IBS. We had a questionnaire based on interview with 120 controls and 124 patients who had shigella infection three years ago. Both groups were evaluated for the presence of IBS, functional bowel disorders (FBD) except IBS before, one and three years after the infection, respectively. RESULTS Ninety-five patients (76.6%) and 105 controls (87.5%) completed the questionnaire. In patients group, 7 cases had IBS prior to infection (previous IBS), 12 cases (13.8%) had IBS after 1 year (PI-IBS). Four cases developed IBS newly after 3 years (new IBS). Thirteen cases (14.9%) in patients and 4 cases (4.5%) in controls had IBS over 3 years (OR 3.93: 1.20-12.86). The recovery rate over 3 years were 50.0% (2/4) in previous IBS and 25% (3/12) in PI-IBS. The incidence of PI-IBS after 3 years in previous FBD subjects was 28.6% and was 10.6% in normals (p<0.05). The female gender was a risk factor for FBD. CONCLUSIONS Bacterial gastroenteritis is a trigger factor of IBS. About a quarter of PI-IBS patients are recovered over 3 years. Previous FBD except IBS is a risk factor after 3 years.