A series of double-blind, parallel, clinical trials was carried out to assess the analgesic and anti-inflammatory effects of tenoxicam and to compare the efficacy and tolerance of this compound with those of piroxicam in patients suffering from osteoarthrosis, rheumatoid arthritis and ankylosing spondylitis. In equivalent once-daily dosage (20 mg), tenoxicam was found to be at least as effective as piroxicam in combating the symptoms of the above arthritic disorders and, even in relatively high dosages of 30 and 40 mg exhibited excellent tolerance, producing fewer adverse reactions than piroxicam. It is concluded that tenoxicam represents a valuable addition to the spectrum of anti-inflammatory agents.