3450 bovine from different breeds and ages were clinically examined for the presence of arthritis. 120 cases showed macroscopic evidences of arthritis. Mycoplasma spp were isolated from synovial fluid of 21 affected animals. In addition to Mycoplasma spp. Arcanobacterium pyogenes and Staphylococcus epidermidis were isolated from 2 cases. The synovial fluid was markedly increased, straw color, turbid and mostly contained thick confluent fibrin. Thickening of the synovial membrane, villus hyperplasia, loss of the synovial cells, infiltration of leukocytes, hyperemia and edema of synovial membrane and periarticulare tissues were seen. Isolation of Mycoplasma from the bovine with arthritis indicates the importance of the organism as causative agent of the disease.