Osteochondritis dissecans occurs most commonly in knee joint and often in elbow, ankle, shoulder, hip than in other joint. In osteochondiritis dissecans, an area of subchondral bone undergoes avascular necrosis and degenerative change ususlly occurs in cartilage overlying it. During the course of disease, unless interrupted by treatment or spontaneous healing, the necrotic bone and cartilage seperates from adjacent bone and cartilage and together becomes loose body. To promote healing, the proper treatment is necessary before degenerative change developes. The authors reviewed 11 cases of osteochondritis dissecans which recieved treatment at Severance hospital from January 1972 to December 1981. The results were obtained as follows: 1. The incidence of osteochondritis dissecans in male was a little more frequent than that of female and 50% were observed in the age of 16 to 30 years. 2. The most common symptom and sign was pain and limitation of motion, instability senastion, tenderness, snapping sound in order of frequency. 3. The most common area involved was the knee in 9 cases, 5 cases involved the medial femoral condyle, 4 cases involved the lateral femoral condyle. The ankle and elbow was 1 case for each. 4. Eight(72.7%) of 11 cases had history of trauma. 5. Among 9 cases of knee inlovement, 5 (55.6%) cases were associated with rupture of meniscus. 6. The methods of treatment were as follows.