A prospective study of the Ring Total Knee Replacement is presented. The senior author (P.A. Ring) designed this prosthesis and began to apply it clinically in 1974. The Ring prosthesis is a resurfacing, unconstrained type of knee prosthesis and is designed for use without cement. It comprises two components, femoral and tibial, both made of titanium. A polyethylene liner is attached to the tibial component. The method was used for treatment of osteoarthritis and rheumatoid arthritis of the knee on 149 patients (178 knees) in the period from 1974 to 1985. Seventeen patients were lost to follow-up, leaving 132 patients (161 knees) for review. During the last review, 75.2% of the knees were pain free and 72% had full correction of the deformity. The average follow-up period was 5.1 years and the survival rate of the prosthesis during the same period was 94.4%. To evaluate the method we used computer analysis of preoperative and postoperative assessment cards with 153 observations. The result was excellent in 92 (57.2%) knees, good in 38 (23.6%) knees, and poor in 31 (19.2%) knees. Loosening of the components occurred in 3.7% knees, and the total revision rate was 5%. One knee was arthrodesed.