Osteoarthritis of the basal joint of the thumb causes pain and disability for a huge segment of the adult population, particularly women. Radiographically, there is a spectrum of disease that has been staged according to severity of involvement of the TM and scaphotrapezial joints. The staging system proposed by Littler and Eaton is used most widely. The severity of clinical symptoms does not necessarily correspond with the radiographic stage of disease, however, so decisions about treatment are predicated upon the notion that we "treat patients, not x-rays." Treatment is based upon the extent to which the pain and functional limitations caused by the disease impact upon the patient's activities of daily living. The evaluation of basal joint disease has been reviewed and modalities of treatment outlined. Conservative treatment includes splinting, nonsteroidal anti-inflammatory drugs, thenar intrinsic strengthening exercise, and corticosteroid injection. Failure of conservative treatment and unremitting pain are indications for basal joint reconstruction by arthroplasty, osteotomy, or arthrodesis. Staging of basal joint disease provides a rationale for selecting the appropriate surgical procedure for a particular patient.