This study was designed to evaluate long-term clinical results after total knee arthroplasty (TKA) with Mark III prosthesis. Among 85 knees which underwent TKA between 1988 and 1995, 33 knees of 25 cases were evaluated by direct examination more than 5 hears after surgery. 21 knees had osteoarthritis (OA) and 12 had rheumatoid arthritis (RA). The mean follow-up period was 10 years (range: 5 years and 5 months to 13 years and 6 months). The range of motion, JOA score, and roentgen graphic findings immediafely after surgery and at final follow-up were evaluated. There was no significant difference between the range of motion soon after surgery and that at the final follow-up. JOA score at the final follow-up significantly improved in both OA and RA cases. Loosening of the femoral components and sinking of the tibial components were identified in 11 and 3 knees respectively, and both were more common in RA cases. Although clinical results were excellent at the mean follow-up period of 10 years, further follow-up is necessary as the incidence of loosening was high (11/33) with this simple and unique Mark III prosthesis.