Between January 1982 and September 1986, at the Department of Orthopaedic Surgery of Kyung Hee University Hospital, 82 total knee arthroplasties were performed in 57 patients. We studied 25 patients (50 Knees) who had been operated by bilateral total knee arthroplasties to compare one stage and two stage operations. The follow-up ranged from 10 months to 5 years and 7 months (average 1 year and 8 months). All operations were performed by one of the authors (D.K.B.), but the follow-up study and the entire medical record were independently evaluated by another authors. The clinical results of preoperative and postoperative assessments and rehabilitation processes are as follows; 1. Group I (10 patients) had both kness replaced by one stage simultaneous operation under same anesthesia, and Group II(15 patients) had replaced by two stage operation at the intervals of 2 weeks. 2. The periods required to do bilateral weight bearing were 10.3 days for Group I, 23.6 days for Group II. 3. Complications in one stage operation was no more than the in two stage operation. 4. The postoperative pain and ROM were not significantly different in both groups. 5. Using the hospital for special surgery rating system, we found the clinical results to be similar in both groups. 6. Comparing to two stage operation, the advantages of one stage operation were shorter operative and tourniquet time, lesser use of antibiotics, reduced medical cost and hospital stay. In conclusion, if patient conditions do not prevent prolonged anesthetic time and surgeons have good surgical techniques, we recommend one stage simultaneous operation in bilateral total knee replacement.