24 cases of synovial chondromatosis were examined including 16 males and 8 females of 22-64 yrs of age. The lesions were located in the knee (16), hip (4) and elbow (4) joints. All cases were treated surgically. The number of cartilaginous nodules and joint mice removed from each joint ranged from 2 to 689. The authors emphasize that the diagnosis could not be definitely established unless multiple foci of cartilaginous metaplasia were found in biopsy of the synovial membrane and that complete removal of cartilaginous nodules and joint mice was essential for successful treatment. Since the disorder is self-limiting, local synovectomy is adequate in most cases and total or subtotal synovectomy is indicated only in cases with extensive synovial membrane involvement. If the synovial membrane is normal, simple removal of joint mice is enough.