PURPOSE: To study the development of inferior shoulder subluxation after surgery for proximal humerus fractures. To analyze the mechanism development of such subluxation and the association between different types of proximal humerus fractures, quality of reduction achieved the method of operation performed. MATERIALS AND METHODS: A retrospective analysis of 45 proximal humerus fractures that were treated by surgery between March 1997 and July 2002 was done. All patients had a minimum of 12 months of postoperative follow up. Preoperative radiographs were classified by the Neer's classification. Different operative treatment methods, post reduction alignment and the degree of postoperative subluxation if present, were analysed. In order to evaluate effect of loss of negative intraarticular pressure, we compared this series with 15 cases of recurrent shoulder dislocation treated by open Bankart operation. RESULTS: 13 patients out of 45 (29%) developed immediate postoperative inferior shoulder subluxation. 3-part fractures of the proximal humerus showed a higher incidence of the same than the 2-part types. The better reduced fractures had lesser rates of subluxation. Open reduction (39%, 11 patients) results in an increased incidence of inferior subluxation than closed methods of reduction (13%, 2 patients). CONCLUSION: Inferior subluxation of the humeral head after surgery for the proximal humerus fracture can occur and persist till postoperative period of 2 months. Deltoid muscle tone affected by shortening of humeral neck plays an important role. Early active exercise for restoration deltoid tone may be effective in prevention of inferior subluxation.