The results of cementless total knee arthroplasty(TKA) have improved steadly during the past decade due to development of design, fixation and surgical technique. We analyzed the results of 45 total knee arthroplasties performed with Anatomic Modular Knee(AMK) prosthesis at the department of Orthopedic Surgery, Yonsei University College of Medicine between June 1989 and December 1991 and compared their results of rheumatoid arthritis(RA) and osteoarthritis(OA) patients. The follow up ranged from 2 years to 4 years and 2 months (average 2 years and 8 months). Using the Hospital for Special Surgery(H.S.S.) rating system and Knee Society(K.S.) clinical rating system, we found that the clinical results were similar for RA group(Average; H.S.S. 86.1, K.S. 81.2/74.4) and OA group(Average; H.S.S. 88, K.S. 87.8/77.1) even though the preoperative knee score was lower in RA group(Average;H.S.S.42.8) than OA group(Average;H.S.S. 57.7). The average age of RA patients was 14 years younger than that of OA patients. The improvement of range of motin and preoperative flexion contracture after TKA was remarkable in RA group. The radiologic evaluation based on Knee Society roentgenographic evaluation system revealed proper alignment of all component and no definite radiologic loosening except 1 case in which postoperative deep infection had occurred. On the basis of this prospective clinical and radiologic review, we concluded that uncemented implantation of AMK prosthsis both in RA and OA patients was encouraging.