Two hundred and forty-five patients who had had 247 primary anterior dislocations of the shoulder were followed for ten years in a multicenter study at twenty-seven Swedish hospitals. The ages of the patients at the time of the dislocation ranged from twelve to forty years. The patients were assigned to one of three treatment groups: immobilization with the arm tied with a bandage to the torso for three to four weeks after reduction of the dislocation; use of a sling, which was discontinued after the patient was comfortable; or immobilization for various durations.At the ten-year follow-up evaluation, no additional dislocation had occurred in 129 shoulders (52 per cent). Recurrent dislocation necessitating operative treatment had developed in fifty-eight shoulders (23 per cent): thirty-four (34 per cent) of the ninety-nine shoulders in patients who were twelve to twenty-two years old, sixteen (28 per cent) of the fifty-seven shoulders in patients who were twenty-three to twenty-nine years old, and eight (9 per cent) of the ninety-one shoulders in patients who were thirty to forty years old. Twenty-four (22 per cent) of the shoulders that had had at least two recurrences during the first two or five years seemed to have stabilized spontaneously without operative intervention at ten years. Dislocation of the contralateral shoulder occurred in association with sixteen (16 per cent) of the ninety-nine shoulders in patients who were twelve to twenty-two years old, twelve (21 per cent) of the fifty-seven shoulders in patients who were twenty-three to twenty-nine years old, and only three (3 per cent) of the ninety-one shoulders in patients who were thirty to forty years old.The type and duration of the initial treatment had no effect on the rate of recurrence.Radiographs, made for 185 shoulders at the time of the primary dislocation, demonstrated an evident Hermodsson (Hill-Sachs) lesion in ninety-nine shoulders (54 per cent); this finding was associated with a significantly worse prognosis with regard to recurrence than was no evident lesion (p < 0.04).Radiographs made for 208 shoulders at the ten-year follow-up examination were evaluated for post-dislocation arthropathy. Twenty-three shoulders (11 per cent) had mild arthropathy and eighteen (9 per cent) had moderate or severe arthropathy. Some of the shoulders that had arthropathy had had no recurrence.