Inflammation and pain, the principal signs and symptoms of arthritis along with swelling and stiffness, are routinely controlled by treatment with a nonsteroidal anti-inflammatory drug (NSAID). Celecoxib, an anti-inflammatory and analgesic agent indicated for the treatment of osteoarthritis and rheumatoid arthritis, is the first cyclooxygenase (COX) inhibitor with well-defined cyclooxygenase-2 (COX-2) specificity. Preclinical studies of celecoxib in vitro and in vivo support the COX-2 hypothesis that the therapeutic effects of NSAIDs are due to the inhibition of COX-2, and the adverse events associated with NSAID therapy are due to the inhibition of cyclooxygenase-1 (COX-1), the constitutively expressed isoform of COX. Clinical trials in patients with osteoarthritis or rheumatoid arthritis found that the efficacy of celecoxib is superior to that of placebo and comparable to that of naproxen, a conventional NSAID. Clinical studies also found celecoxib to be safe and well tolerated, with no evidence of alteration in platelet aggregation or gastrointestinal ulceration.