Epileptic seizures can cause shoulder dislocation and instability, but a characteristic pattern of instability and structural lesions is not well known. We reviewed 34 shoulders in 26 patients in whom the initial dislocation had been caused by an epileptic seizure. All patients were followed up clinically and radiologically for a mean of 10 years (range, 2-21 years) after initiation of treatment. Thirteen patients (17 shoulders) were treated for anterior instability. A large Hill-Sachs lesion was found 12 times and a large glenoid rim fracture 5 times. There were 12 recurrent and 2 locked dislocations. The recurrence rate after the first repair was 47% (8/17 shoulders). The final overall results at a mean follow-up of 10 years (range, 2-12 years) were good in 12 cases, satisfactory in 2, and unsatisfactory in 2. The reoperation rate was 40%. With skeletal reconstruction, 12 of 13 shoulders were stable at final follow-up. Another 13 patients (17 shoulders) were treated for posterior dislocation. A large reverse Hill-Sachs lesion was observed 13 times and a posterior glenoid rim fracture twice. There were 15 locked but only 2 recurrent dislocations. The recurrence rate after repair was 12% (2/17 shoulders). The final outcome at a mean follow-up of 7 years (range, 2-12 years) was good in 11 shoulders and satisfactory in 6. The reoperation rate was 12%. Anterior and posterior dislocations occurred with equal frequency in this series. Large bony lesions were the hallmark finding in this group of patients. Skeletal reconstruction was necessary to obtain clinical stability, especially in the more difficult-to-treat anterior instability.