Previous studies on arthroscopic treatment of anterior-inferior glenohumeral instability have focused on the repair of lesions of the anterior-inferior aspect of the labrum (Bankart lesions) and have demonstrated failure rates of as high as 50 percent. The current investigation supports the concept that anterior-inferior instability is associated with multiple lesions and that success rates can be increased by treating all of the lesions at the time of the operation. We present the results of arthroscopic treatment of anterior-inferior gleno-humeral instability after a minimum duration of followup of two years. The study group consisted of fifty-three patients who had a mean age of thirty-two years (range, fifteen to fifty-eight years) at the time of the operation. There were forty-four male and nine female patients. The mean interval from the time of the operation to the final follow-up evaluation was thirty-three months (range, twenty-six to sixty-three months). The scores on the American Shoulder and Elbow Surgeons (ASES) Shoulder Index and the rating systems of Constant and Murley, Rowe et al., and the University of California at Los Angeles (UCLA) were recorded preoperatively and at the time of the final follow-up. Preoperatively, none of the patients had an overall rating of good or excellent according to the system of Rowe et al.; however, 92 percent (forty-nine) of the fifty-three patients had a rating of good or excellent at the time of the final follow-up. The mean score improved from 45.5 points to 91.7 points on the ASES Shoulder Index, from 56.4 points to 91.8 points with the system of Constant and Murley, from 11.3 points to 91.9 points with the system of Rowe et al., and from 17.6 points to 32.0 points according to the UCLA Shoulder Score (p = 0.001 for all comparisons). The mean passive external rotation with the shoulder in 90 degrees of abduction measured 88.2 degrees. Thirty-four of thirty-eight patients returned to their desired level of sports activity following the operation. Four patients who had persistent instability were considered to have had a failure of the index operation, and one of them had a second operative procedure. The results of the present study suggest that our technique of arthroscopic treatment of anterior-inferior glenohumeral instability is better than previous arthroscopic techniques and is equivalent to open repair. We believe that the improved rate of success demonstrated in the present study was the result of repair not only of the anterior-inferior (Bankart) lesion but also (where necessary) of inferior and superior labral tears. Additionally, soft-tissue tension within the capsule and ligaments was corrected with use of a suture technique but was supplemented by laser thermal capsulorrhaphy in forty-eight of the fifty-three shoulders. Rotator interval repair was considered a critical factor in fourteen of the fifty-three shoulders.