Polycentric total knee arthroplasty has been performed at the Mayo Clinic on more than 1,600 knees since July 1970. Two groups of 106 and 101 knee arthroplasties performed between July 1970 and July 1971 and June 1971 and January 1972, respectively, were compared at 5 and 7 years. The technique used exposed the joint to methacrylate particles, yet, despite this, wear did not prove to be a problem. Failures occurred because of infection, loosening of the tibial components, settling of the tibial components, subluxation or dislocation, ligamentous laxity, progression of patellofemoral arthritis, and persistence of pain. We did not encounter patellar problems in our patients with osteoarthritis. In the first group with 106 knees, 45 patients with 58 rheumatoid knees survived 7 years; 79% of knees had good results at 5 years and 72% had good results at 7 years. Twenty-one patients with 28 osteoarthritic knees survived 7 years; 75% of knees had good results at 5 years and 61% had good results at 7 years. In group 2 with 101 knees, 43 patients with 64 rheumatoid knees survived 7 years. The results were good in 83% at 5 years and in 64% at 7 years. Among the 20 patients with osteoarthritic knees who survived 7 years, 92% of knees had good results at 5 years and 62.5% had good results at 7 years. This figure is somewhat misleading because 7 patients were lost to follow up in group 2 after 5 years. There is still a need for a well-tolerated resurfacing procedure by means of a nonconstrained prosthesis.