The results of total knee arthroplasty (TKA) have improved steadily during the past decade due to refinements in design, fixation and surgical technique. We studied the results of 70 total knee arthroplasties performed at the department of Orthopaedic Surgery, Catholic University Medical College Kangnam St. Mary's Hospital during September 1982 to March 1990, to compare the results of rheumatoid and osteoarthritic patients. The follow up ranged from one year to eight and half years average being three years and four months. Using the Hospital for Special Surgery rating system we found that the clinical results to be identical for rheumatoid (average; 87.3) and osteoarthritic patients (average; 86.6), even though the preoperative knee score was lower in rheumatoid patients (average; 33.8) than that of osteoarthritic patients (average; 44.2). Thirteen patients of younger age group (21 to 50 years) were rheumatoid arthritis compared to the 28 (80%) out of 35 patients were osteoarthritic in elder age group (51 to 80 years). The number of bilateral TKA was much higher in rhemuatoid patients (70 % ) than osteoarthritic patients(28%). The improvement of range of motion after TKA was greater in rheumatoid arthritis (average 86°preop. to 180°postop.) than osteoarthritis (average 114°preop. to 125°postop.). Preoperative flexion contracture was more severe in rheumatoid arthritis (average 21°) than osteoarthritis (average 9°) but after TKA the average degree of flexion contracture was no significant difference (R.A: 8°, O.A: 5°) beween two groups.