Arthritis induced in rats by a mycobacterial adjuvant has been usen for the comparative study of efficacy of calcium bucloxate (CB), phenylbutazone (PB), indomethacin (TM) and hydrocortisone (HC). The change in volume of hind-foot joint was measured with a glasscylinder after the arthritic syndrome has developed in the treated animals. On the 20th day of the experiment the arthritic tarsal joints were removed for histopathological study. CB showed strong inhibitory activity on inflammation at the first and second stages. The anti-arthritic effect of CB was better than that of CH and was equal to, or somewhat better than, that of PB. Better therapeutic effect was observed in the group administered 50 mg/kg of CB than in the animals given IM 1 mg/kg.