We reviewed the cases of fifty-six scaphoid non-unions in fifty-five patients, none of whom had received treatment of any kind before examination. In the thirty-two patients who had been injured five years or more earlier, arthritis developed in thirty-one (97 per cent). The one patient in whom osteoarthritis developed less than four years after injury also had avascular necrosis of the scaphoid. The incidence of osteoarthritis increased with time after injury. We concluded that patients with established scaphoid non-union should be advised that osteoarthritis will most likely develop.