Naproxen is a propionic acid derivative with analgesic and anti-inflammatory activity which has been widely used in the treatment of rheumatic diseases. Naproxen has been well studied in rheumatoid arthritis and is as effective as aspirin but better tolerated, thus enabling more patients to continue with treatment. For this reason some clinicians now prefer to try propionic acid derivatives, such as naproxen, before aspirin in arthritic patients. In comparative studies with other non-steroidal anti-inflammatory drugs, such as indomethacin, ibuprofen, fenoprofen and others, all drugs were usually of similar overall efficacy although naproxen was sometimes preferred: but as with other non-steroidal anti-inflammatory agents, not all patients will respond to naproxen and in such cases other agents should also be tried until the most satisfactory drug is found for each patient. Naproxen is also effective in degenerative joint diseases of the hip and knee, although further well designed studies are needed to more clearly define its relative place compared with newer drugs such as diclofenac or diflunisal. Results of other comparative studies have shown that naproxen is a suitable alternative to phenylbutazone or indomethacin in ankylosing spondylitis and to aspirin in juvenile rheumatoid arthritis. Naproxen appears to be effective in reducing pain and swelling in acute gout and is an effective analgesic in patients with pain following surgery or trauma and in pain of dysmenorrhoea. Naproxen has generally been better tolerated than aspirin or indomethacin at the dosages used. Because of its relatively long plasma half-life, naproxen can with convenieice be given twice daily, and there is some evidence that once daily dosage is as effective in rheumatoid arthritis.