Proquazone is a non-steroidal anti-inflammatory agent (NSAID) which, unlike most other NSAIDs, does not have a free acid group in its structure. It is advocated for use in rheumatoid arthritis, ankylosing spondylitis, osteoarthritis, musculoskeletal disorders, acute inflammatory conditions and acute pain states such as dysmenorrhoea, postoperative pain and headache. Published data in small groups of patients indicate that proquazone 300 to 900 mg/day in 3 divided doses is a possible alternative to aspirin, ibuprofen, indomethacin, and naproxen in rheumatoid arthritis, and to indomethacin and ibuprofen in ankylosing spondylitis. Similarly, proquazone 300 to 900 mg/day is as effective as aspirin, diclofenac, ibuprofen, indomethacin and naproxen in patients with osteoarthritis. Preliminary studies have confirmed the efficacy of proquazone in acute inflammatory disorders, and shown that it provides useful analgesic relief in acute pain states such as dysmenorrhoea, headache and after minor surgery. Evidence from small groups of patients with rheumatoid arthritis treated for a year or more suggests that proquazone may inhibit or arrest progression of bone erosions. However, these encouraging findings clearly need confirmation in a larger number of patients studied under well-controlled conditions. The overall impression from clinical trials to date is that proquazone at dosages of greater than or equal to 900 mg/day produces a high incidence of gastrointestinal symptoms such as diarrhoea (in approximately 30% of patients). However, these effects were usually of mild to moderate severity and transient in nature and in most comparative studies the overall tolerability of proquazone was assessed as being comparable to that of other NSAIDs tested. Similarly, withdrawal from therapy due to side effects was no greater with proquazone than with other NSAIDs evaluated. Initial experience with lower dosages of proquazone (300 to 450 mg/day) suggest that efficacy is maintained and tolerability markedly improved. Thus, at present, proquazone would seem to be as effective as other NSAIDs used in the management of rheumatoid arthritis and osteoarthritis. However, further studies are needed to fully evaluate the efficacy and tolerability of this agent, especially at the lower daily dosages currently recommended, and to clarify whether it does have significant 'disease modifying' potential.