We reviewed 90 cases of popliteal cyst in 88 patients, managed at Department of Orthopedic Surgery, Severance Hospital from January 1976 to June 1985 and the following results were obtained. 1. The average age of the 88 patients was 42 years. There were 23 males and 65 females. Of the all patients, 47 were occured in right side and 39 the left. Two patients were both sides. 2. Of the all cysts, 62 were found to be bursa between the semimembranosus and the medial head of the gastrocnemius muscles(68.8%). 3. Associated adnormalities of the knee joint were apparent in 29(33%) and the most common abnormalities were osteoarthritis. 3. Associated adnormalities of the knee joint were apparent in 29(33%) and the most common abnormalities were osteoarthritis. 4. Communication of the cyst with the joint was apparent in 44 cases(49%). 5. Twelve patients were recurred and associated abnormality of the knee joint was osteoarthritis. Three patients were children and they had no abnormality of the knee joint. 6. Recurrence after primary operation was rare when the stalk of the cyst had been opened.