Between 1980 and 1994, 221 shoulders with recurrent anterior glenohumeral subluxation or dislocation were reconstructed at our institution. At the time of the operation, thirteen shoulders were found to have an irreparable injury of the subscapularis muscle, which we believed to be a contributing factor to the ongoing instability. All but three of the thirteen patients had had two to six previous reconstructions. Operative treatment of the irreparable rupture included a dynamic muscle transfer using the pectoralis major in seven shoulders, the pectoralis minor in five, and both of these muscles in one. According to a modification of the grading system of Neer and Foster, the result was satisfactory for ten shoulders and unsatisfactory for three at a mean of five years after the operation. All shoulders with a satisfactory result demonstrated active contraction of the transferred pectoralis muscle and diminished anterior glenohumeral translation. On the basis of our analysis, we concluded that transfer of the pectoralis muscle is effective for reconstruction of the shoulder in patients who have loss of the subscapularis muscle.