This type of endoprosthesis was used for four years in chronically painful idiopathic osteoarthritis of the carpometacarpal joint of the thumb. Our results match exactly those published by the originator of the endoprosthesis CAFFINIERE, i.e. 70% excellent results, nearly 30% problem cases. The problem of loosening of the stem or the cup of the prosthesis seems to depend in our cases on the operative technique rather than on the design or other factors. In the rheumatoid patient as well as in polyarthrotic hands we cannot encourage the prosthetic replacement of the carpometacarpal joint of the thumb.