Pigmented villonodular synovitis and synovial chondromatosis are known as a poup of interrelated tumorous disorders that involve the lining of the joints, hursa and tendon sheath. Pigmented villonodular synovitis consists of proliferatin synovia1 tissue containing histiocytes, librohlasts, multinucleated giant cells, and capillaries that can destroy dense fihrous tissue, form soft tissue masses, and invade bone. Synovial chondromatosis consists of hyaline cartilage nodules within the synovium and synovial joint cavities, develop multiple loose fragments of cartilage within the joint. They may represent a reactive inflammatory process or henign neoplasm and usually occur in latge synovial joints, including the knee, hip and ankle. There are some reports stating that pigmented villonodular synovitis has coexisted with synovial chondromatosis. but none have reported that they occurred simultaneously in a large single joint. This is a report on a diagnosed and arthroscopicully treated pigmented villonodular synovitis and synovial chondromatosis that occurred simultaneously in the same ankle joint.