An open label study was carried out to assess the long-term use of acemetacin in patients suffering from rheumatoid arthritis. One hundred and two patients were treated with acemetacin, some patients for up to a 12-month period. Analysis of efficacy showed that acemetacin therapy was associated with statistically significant sustained improvements in the target variables of duration of morning stiffness, Ritchie articular index and left and right grip strength. With regard to tolerability, a number of adverse events were recorded but were generally reported as either mild or moderate. In total, 28,988 patient days' treatment with acemetacin were completed and acemetacin proved an effective and well-tolerated long-term therapy in patients with rheumatoid arthritis.