Sixty-six Freeman-Swanson arthroplasties were performed on 59 patients with rheumatoid arthritis from 1972 through 1979. The patients were followed prospectively and longitudinally. Thus, a detailed protocol was filled out preoperatively and once a year thereafter. This report is based on a total of 299 observations, with a follow-up period ranging from 2 to 7 years (mean 4.4 years). Pain was the main indication for surgery and relief of pain the most gratifying and consistent finding over the years. Of 56 knees remaining in the study in 1979, 61 per cent were considered to be good, 27 per cent satisfactory, and 12 per cent were failures. Early complications were observed in 20 per cent of the knees, late complications in 24 per cent. The majority of the complications resolved after treatment but six knees (9 per cent) deteriorated following a late complication. Thirteen reoperations were performed, of which five were prosthetic revisions. In conclusion, the results were good over a 7-year period provided the deformity was corrected, stability restored and the prosthetic components positioned perpendicular to the mechanical axis of the leg. Tibial component loosening was the most important reason for failure.