From 1993 to 1996, we have used a new modular shoulder prosthesis for the treatment of acute complex fracture of the proximal humerus. The purpose of this study is to evaluate function, pain relief, and patient satisfaction after moduiar hemiarthroplasty for proximal humerus fractures. The stucly included 12 patients (J2 shoulders) with an average age of 68.5 years (range, 60 to 84 years). According to the Neer classification system, there were 3 four-part fracture-dislocations, 5 four-part fractures, 3 three-part fractures, and #I head splitting fracture. 'fhe hemiarthroplasty was pert'ormed at an average of 4 days (range, 3 to 10 days) following injury. Deltopectoral approach was used in all patients, and the prostheses were implanted with cement in ten cases. Follow-up evaluation, at an average of 32 months post-surgery, included clinical and radio- graphic examination. Active forward elevation averaged 120 degrees; external rotation, 35 degrees; and internal rotation, to the first lumbar vertebra. All of patients, except two who had poor results, were graded as good or excellent according to UCLA shoulder rating scale. Complications consisted of one tuberosity dispiacement, one peri-operative death and one loosening of uncemented humeral prosthesis. We concluded that Modular hemiarthroplasty for acute complex fracture of the proximal humerus especially in severely osteoporotic elderly patients facilitated the restoration of humeral length, anatomic repositioning of tuberosities, and precise soft tissue balance, thereby allowing earliermotion to prevent the developement of painful shoulder stiffness.