Between December 1982 and November 1985, fifteen unicompartmental prostheses were implanted in eleven patients at the department of orthopedic surgery, Kyung Hee university. Modular II unicompartmental prostheses were used in fourteen knees and Oxford prosthesis in one knee. The average age at operation was 61 years old (range;50-76 years old) and average follow-up period was four years and six months. Functional assessments, including rating by the Hospital for Special Surgery knee score and radiographic evaluation of radiolucency were conducted. The results of clinical and radiological analysis are as follows;1. The preoperative diagnosis was osteoarthritis in fourteen knees and osteonecrosis in one knee. Thirteen knees had undergone medial compartmental arthroplasty and two knees had undergone lateral compartmental arthroplasty. 2. The average preoperative range of motion was 124 degrees and the average postoperative range of motion was 125 degrees. So, the average postoperative range of motion was similar to the average preoperative range of motion. 3. The average tibiofemoral angle was corrected from valgus 2.5 preoperatively to valgus 4.5 postoperatively. 4. The average preoperative knee rating score was 46.5 points and postoperatively the average score improved to 88 points. 5. There were no deep infection, Mild knee pain was noted in one knee and incomplete radiolucencies less than 1mm width at the bone cement interface on the tibial side were noted in two knees.