The efficacy and tolerability of Timegadine, a new antirheumatic agent, administered at a dose of 250 mg twice daily was evaluated in an open trial of 24 weeks' duration in 31 patients with active rheumatoid arthritis. The subjective and objective clinical parameters improved significantly from the 2nd to 6th week of treatment. For some of the parameters further improvement was observed during the continuation of the treatment. At 6 weeks the ESR was significantly decreased, and a further reduction of the ESR was seen with the continuation of the treatment. At the end of the treatment period other humoral parameters of the disease were significantly modified. Moreover, in 65% of the patients with seropositive rheumatoid arthritis a reduction of the rheumatoid factor titre by at least two dilutions was observed. Five of the 31 patients were withdrawn from treatment due to the appearance of side effects. Although the study was open and the number of patients relatively small, the observed changes in the laboratory parameters of disease activity encourage further investigations to assess the potential of Timegadine as a remissive drug.