OBJECTIVES: Crohn's disease (CD) is a potentially expensive disease as it is a chronic, not curable condition with high hospitalisation rates. The objective of the study was to estimate the healthcare resource use and epidemiology in a large UK population. METHODS: This was a retrospective study using NHS inpatient data (HES data) from 2001 over a period of 5 years representing England (population in 2001 49,140,000). To compare these results data from the region of Cardiff, Wales, UK (population in 2003 approximately 434,000) was used. This data contains inpatient, outpatient, biochemistry and mortality data over a period of at least 12 years that has undergone record linkage. Patients included were those with a diagnosis of CD (ICD-10 K50*) as cause of admission. Number, type and method of admission, incidence and survival were analysed. HRGs were used to calculate inpatient costs. RESULTS: A total of 18,573 patients were identified in the NHS data [644 Cardiff data], of whom 7,666 (41.3%) [250 (38.8%) Cardiff data] were male. The average incidence was 14 per 100,000 per year. Mean length of stay for primary index admissions was 9.2 (SD 14.7) days and mean costs £2304 (SD £2778). Re-admission rates (primary or secondary ICD code) in the year after index admission were 1.36 (SD 3.26) and disease related 0.83 (SD 2.34) per patient; average length of stay per admission were 6.5 (SD 14.6), average costs £1776 (SD £2692). Surgery rate in the year after index admission was 0.16 (SD 0.46); average length of stay 12.5 (SD 22.1), average costs per surgery £4048 (SD £4158). The rates declined over the follow-up years. Hospital days, costs and rates approximately matched the Cardiff data, but were slightly higher. CONCLUSION: This study provides epidemiological and resource use information on patients with CD. It confirms the high resource use and gives insight into determinants.