OBJECTIVES: Irritable bowel syndrome (IBS) is a relapsing, chronic functional gastrointestinal disorder with continuous nuisance bowel symptoms leading to long-term disturbances to patients. The disease burden of long-term IBS, however, is generally neglected in Taiwan. This study aimed to evaluate medical and drug utilization for IBS outpatients receiving long-term medical treatments in Taiwan. METHODS: This cross-sectional study was conducted from 2004 to 2008 using a Longitudinal Health Insurance Database constituting of a million beneficiaries randomly sampled in 2005. Adult IBS outpatients' medical claims and prescriptions data were extracted and medication possession ratio (MPR) was calculated based on anti-IBS prescriptions (i.e. anti-propulsive, anti-spasmodics, propulsive, anti-depressive agents and laxatives). Patients whose accumulated prescription duration for more than 90 days and MPR>80% were included as study cohort and their medical and drug utilization were assessed. Monthly trends of medical and drug utilization were analyzed by simple linear regression and stratified by gastroenterology specialists and tiers of medical facilities. RESULTS: Only 1451 (3.5%) patients were included, but this cohort (mean age 60.8±16.7 years; 54.0% male) contributed to 20913 visits, 20.3% medical cost and 70.5% drug cost of the 40890 IBS outpatients. Number of outpatient visits and total medical cost in study cohort significantly increased over time (p<0.01), particularly in regional hospitals. Number of visits to non-gastroenterology (10471; 50.1%) and gastroenterology specialists were similar, but monthly trend of gastroenterology visits significantly increased (p<0.001) in different tiers of medical facilities. Antispasmodics (13904; 41.0%) and laxatives (9240; 27.2%) were the most frequently prescribed and monthly consumptions of antipropulsive, antispasmodics and propulsive significantly increased (p<0.001) over time. CONCLUSIONS: A small cohort of outpatients receiving long-term IBS treatments contributed to 20% of all IBS outpatient expenditure. As their medical utilization and cost are substantially increasing, further economic evaluation is needed to inform resource allocation decisions in the future.