60 type MOTORLET knee joint endoprostheses are evaluated in this paper. Endoprostheses were implanted in the years 1984-1986 to 51 patients with rheumatoid arthritis and osteoarthrosis of the knee joint. EULAR knee project questionnaire was used to evaluate the results. In 72% of patients the pain completely disappeared both at rest and in movement. The average range of movement, ability to walk and knee joint stability were significantly improved, with highly favourable evaluation in 90% of operated patients. All parameters were compared with the results of 1569 knee joint operations evaluated within the range of EULAR knee project. At the same follow-up period the endoprosthesis type MOTORLET has been comparable to other widely used knee joint replacements.