OBJECTIVES: This study investigates the extent to which IBS imposes a financial burden on an employer. METHODS: Administrative claims data from a national, Fortune 100 manufacturer that includes all medical, pharmaceutical, and disability claims for the company's employees, spouses, dependents, and retirees (n>100,000) were used for this analysis. IBS patients (n=1,610) were identified using ICD-9-CM codes of individuals aged 18 through 64 years, who received primary treatment for IBS; or secondary treatment for IBS and primary treatment for constipation or abdominal pain, between 1996 and 1998. Over 93% (N=1,509) of these IBS patients were matched based on age, sex, zip code, and employment status to control beneficiaries. Excluded from both the IBS and control samples were patients treated for malignant neoplasm of digestive organ and peritoneum, inflammatory bowel disease, Crohn's disease, ulcerative colitis, and diverticulitis. Direct (medical and pharmaceutical) and indirect (disability and medically-related work absence) costs of IBS patients and controls were estimated using SAS, version 8. RESULTS: On average, an IBS patient cost the employer $1,251 more than an employee not treated for IBS ($4,527 versus $3,276; p<0.0001). Direct medical costs accounted for 83% of total costs associated with IBS. Hospital outpatient costs accounted for the largest portion; average hospital outpatient costs were $1,258 and $742 for IBS patients and controls, respectively (p<0.0001). The average number of medical claims per IBS patient was 17.4 versus 10.9 for controls (p<0.0001). The average number of prescriptions filled was 26.9 versus 19.2 for IBS patients and controls respectively (p<0.0001). Medically-related work absence costs were $301 and $176 for IBS patients and controls, respectively (p<0.0001). CONCLUSIONS: IBS patients impose a significant financial burden on the employer, due to higher levels of medical and pharmaceutical care utilization and medically-related work absences compared to controls.