In osteoarthritis of knee, sensitive and reproducible methods of evaluation are of particular importance in unicompartmental surgery, in which choice of technique and prognosis depend on accurate preoperative knowledge of distribution and extent of disease. The various diagnostic modalities for evaluation of osteoarthritic knee are present but it is known that Tc-99m-MDP scintigraphy is the most sensitive and noninvasive method. The authors, made a comparative study of scintigraphic findings and radiographic findings of 54 cases of osteoarthritic knees at Kyung Hee University Hospital from May '83 to August '85. The results were as follow: 1) Tc- 99m-MDP scintigraphy appeared more sensitive not only in detection of abnormal compartment but also in evaluation of severity of the diseased compartment compared to radiography. 2) We suggest that bone scintigraphy is most sensitive for preoperative information of extent and severity of the disease related to surgical technique and prognosis.