Painful arthrosis of the basal joints of the thumb covers a spectrum of arthritic disease. The painful hypermobile thumb with articular cartilage preserved requires an entirely different type of treatment than does the similarly painful basal joint, which has stiffness and degeneration of more than one facet of the trapezium. By careful radiographic evaluation of the trapezial articulations, particularly in the lateral projection, a reasonable set of radiographic guidelines for staging of the degenerative process can be provided. One must be prepared to adjust this preoperative staging should direct inspection of the articular surfaces at surgery indicate more damage than perceived on the radiograph. Once the ultimate staging of the disease has been established, the means of treatment is considerably simplified and the multiple procedures that have been proposed for "basal joint arthritis" can be applied more accurately.