Chondroblastoma is a rare primary neoplasm of bone which involves the epiphysis of the long bone and develops mostly in the 2nd decade of life. We reviewed the cases of twenty patients with chondroblastoma who were treated at the Department of Orthopaedic Surgery, Yonsei University College of Medicine between 1969 and 1989. All patients were followed for 1 year or longer. The results were as follows. 1. The proximal end of the humerus(25%) and the proximal end of the femur(25%) were the most common sites. 2. 85% of patients were between 11 to 20 years old and male to female ratio was 3:2. 3. The most common symptom was pain and in 30% of patients it was appeared after minor trauma. 4. The average diameter of lesion is 4.2cm in its long axis and the more longer the duration, the more larger the size of lesion. 5. Involvement of the epiphyseal plate was twice as common in the patients with a closing plate as in those with an open one. 6. The most common microscopic finding was the presence of chondroblast and chondroid matrix. 7. Two patients(10%) had a local recurrence. 8. The final functional results were considered to be good in sixteen(80%) patients. 9. Accurste localization of the lesion during biopsy is very important especially in the case of deep seated lesion.