In patients disabled by severe rheumatoid and degenerative arthritis of both knees, bilateral total knee arthroplasty(TKA) afforded much functional improvement in pain relief and function. Postoperative results of bilateral TKA was described as being similiar to those observed among patients with single joint replacement. The purpose of this study is to evaluate the etiology and postoperative result of bilateral TKA performed on 32 knees in 16 patients at Department of Orthopedic Surgery, Seoul National University Hospital from Mar. 1985 to Oct. 1988. In our series, there were 15 females and only 1 male, their mean age was 53 years. Duration of follow up was ranged from 1 to 4 years and 5 months being average 1 year and 6 months. The results were as follow. 1. Cheif complaints were pain in 18 cases(100%) and difficulty in walking in 15 cases(82%). 2. Preoperative etiology was rheumatoid arthritis in 11 cases and degenerative arthritis in 7 cases. 3. Knee joint function by HSS(Hospital for Special Surgery) knee rating score was increased from 44.6 points preoperatively to 81.2 points postoperatively. 4. The tibiofemoral angle was changed from 1.4 degree varus to 4 degree valgus. 5. The prothesis type used were PFG(Press Fit Condylar) in 22 knees, Miller-Galante in 8 knees, AMK in 3 knees, PCA in 2 knees and unicompartmental type in 1 knee. 6. Complication were 1 case of knee fusion due to concomittant tuberculous arthritis and mild joint effusion in 6 knees. 7. Bilateral one-stage arthroplasty may be considered as an alternative procedure.