In this double blind, randomized, parallel group study, 298 patients with rheumatoid arthritis received nabumetone (2000 mg/day) or naproxen (1000 mg/day) for 3 months. At the end point, nabumetone treated patients exhibited significant improvement in pain, Ritchie articular index, and duration of morning stiffness when compared to baseline. In contrast, naproxen treated patients showed significant improvement only in Ritchie articular index. Nabumetone was significantly more effective than naproxen for pain relief. More nabumetone treated patients withdrew due to lack of efficacy than naproxen treated patients. However, nabumetone was better tolerated than naproxen because fewer patients withdrew for adverse events or experienced severe adverse events, and significantly fewer patients required treatment for adverse events.