The effectiveness of etodolac in the treatment of patients with osteoarthritis (OA) and with rheumatoid arthritis (RA) has been well documented in controlled clinical trials. The superiority of etodolac, 300 mg twice daily, over placebo has already been established in short-term trials involving patients with OA. During long-term treatment, significant (p < 0.05) improvement was observed in patients with OA and RA as measured by a variety of efficacy parameters. In comparative studies for OA, etodolac was more effective than conventional indomethacin; naproxen, sustained-release diclofenac, and piroxicam were comparably effective. The newer sustained-release formulation of etodolac is as effective as the conventional etodolac formulation when used to treat patients with OA and those with RA.