Nabumetone, belonging to a new class of anti-inflammatory drugs, was administered to 9 patients suffering from radiologically-confirmed osteoarthritis of one or more of the following articulations: knees, hips, cervical and lumbar spine. A single nightly dose of 1 g was given for at least one year, and up to three years. The drug was found to be generally effective on such criteria as articular mobility, night pain, and pain during activity. No significant alterations which could be attributed to the treatment were seen in haematological parameters, blood creatinine and urea levels, protein, transaminases, alkaline phosphatase, gamma-glutamyl transferase and other blood and urine tests. The side-effects claimed by the patients included gastric upset, pyrosis, epigastric pain, constipation, malleolar oedema and drowsiness. These complaints did not lead to termination of the treatment. The efficacy and safety of nabumetone found in this and other studies warrant its further investigation in the treatment of rheumatic diseases.