Studies have demonstrated the beneficial effects of fangotherapy on relieve of pain improving function of rheumatic patients. Herein, we investigated the effect of Brazilian black mud in protect articular damage in chronic arthritis induced in rats. Mud was daily applied (40 degrees C/30 min) during the course of arthritis and was compared with warm water and no treated groups. At 21th day after arthritis induction synovial fluid and membrane were analyzed regarding cellular influx, hyperplasia and vascular proliferation. Cartilage structure, cell count, proteoglycan and collagen amount were also analyzed by three pathologists blinded to the treatment. Mud treatment diminished leukocyte migration into the synovial membrane and articular cavity when compared with both control groups. Regarding cartilage, an increase in collagen, number of chondrocytes and more conserved tissue structure was observed in mud-treated animals. These results demonstrate a protective effect of Brazilian mud on this model of arthritis, suggesting that this therapy may be useful as a complementary approach to treat articular diseases.