The purpose of this assessment is to evaluate the long-term cost-effectiveness of the COX2 NSAID celecoxib, in comparison to diclofenac and ibuprofen, and rofecoxib in comparison to naproxen, in patients with OA and RA who are not on low-dose aspirin for the prevention of CV disease. Analyses are performed for patients at average risk of upper gastrointestinal (UGI) events, and for higher risk patients with a history of a UGI event that is either (a) a clinical UGI event (a symptomatic ulcer), as shown by endoscopy, or (b) a complicated UGI event (a GI perforation, obstruction or major bleeding).