Of 780 patients treated for primary anterior shoulder dislocations, 33 (4.2%) were aged 12 to 17 years at the time of the dislocation. We clinically evaluated 28 of these patients a mean of 7.1 years after the initial dislocation. All patients were radiographed, and 15 underwent magnetic resonance imaging or computed arthrotomography of the shoulder. The primary dislocation had been traumatic in 21 patients (75%) and atraumatic in 7 patients (25%). Recurrent dislocations had occurred in 24 cases (86%), the number of recurrences ranging from 1 to 30. In the group with traumatic primary dislocations, the rate of recurrences was 92% and the mean number of redislocations was 7 in the patients who had been 14 to 17 years of age at the time of the initial injury, whereas the corresponding figures were 33% and 0.3 in the patients who had been 13 years of age or less at the time of the initial injury. Imaging studies showed a Bankart lesion in 80% of cases; each of these patients had had a traumatic primary dislocation and was 14 to 17 years old at the time of injury. During the follow-up period, operative stabilizing procedures had been performed in 7 cases. At follow-up evaluations, all nonoperated patients showed clinical evidence of anterior or multidirectional instability of the involved shoulder; of the operated patients, each of those with traumatic primary dislocations reported no recurrences and had a satisfactory result, whereas both of the patients with atraumatic primary dislocations continued to have subluxation and/or dislocations of the operated shoulder. In the 14- to 17-year-old adolescents with traumatic primary dislocations in whom imaging studies show Bankart lesions, there is an indication for prophylactic stabilizing surgery at the time of the initial injury.