OBJECTIVES: To evaluate the impact of anti-tumor necrosis factor (anti-TNF) therapy on real world healthcare resource utilization in patients with immune-mediated inflammatory diseases (IMIDs). METHODS: Three groups of patients were identified using claims data from Blue Cross Blue Shield health plans: IMID (rheumatoid arthritis, ankylosing spondylitis, Crohn's disease, psoriatic arthritis, psoriasis or ulcerative colitis) patients receiving anti-TNF therapy between January 1, 2003 and June 30, 2005 (Group 1); IMID controls without anti-TNF therapy (Group 2); and non-IMID controls (Group 3). The groups were matched for gender, age and geographic region in a 3:1 ratio. All patients had >= 6 months continuous plan enrollment before and >= 12 months after the index date. Healthcare resource utilizations per patient per month (PPPM) were calculated for the 6-month pre- and 12-month post-index periods. Differences from baseline were compared among three groups. RESULTS: After matching, 27,006 patients (3,970 Group 1; 11,718 Group 2; and 11,318 Group 3) were analyzed. Of these, 61% were female and the average age was 46 years. Group 1 had higher pre-index PPPM resource utilization for all categories than the 2 control groups. However, compared with pre-index utilization, all post-index resource utilization categories, except emergency room visits, showed a significant decrease for Group 1 that was not consistently observed for controls. Inpatient admissions were reduced in Group 1 (-16.28%), versus no change in Group 2, and +4.17% for Group 3. Physician visits were reduced in Group 1 (–5.11%) versus +2.73% in Group 2, and +6.24% for Group 3. Non-anti-TNF prescriptions were reduced in Group 1 (-6.70%) versus +6.75% in Group 2, and +8.02% for Group 3. CONCLUSION: Anti-TNF therapy appears to be associated with a decrease in healthcare resource utilization. Additional analyses to determine the effectiveness of anti-TNF therapies in patients with IMIDs through clinical, economic, and humanistic assessments are recommended.