Proximal humerus is the common site for primary bone malignancies that surgical treatment consists of wide excision of the tumor and reconstruction with tumor resection prosthesis or allograft. The ultimate function of the shoulder depends on the degree of sacrification of adjacent structures. Thirty-two patients with primary malignancies have been treated by wide excision and endoprosthetic replacement by senior author between 1989–2005 12 patients were female, 20 patients were male, mean age was 26,6 years (range 7–69 years). Histological diagnosis was 14 osteosarcoma, 4 Ewing’s sarcoma, 4 chondrosarcoma, 3 parosteal sarcoma, 4 giant cell tumor, 1 aneurysmal bone cyst, 2 synovial sarcoma. Synovial sarcoma, osteosarcoma and Ewing’s sarcoma patients received neoadjuvant chemotherapy prior to excision. Mean follow-up was 50,4 months (range 6–153 months). Oncologic results were 20 patients NED (no evidence of disease), 2 patients AWD (alive with disease), 10 patients DOD (died of disease). Functional outcome was scored according to Musculo-Skeletal System Tumor Society (MSTS) rating scale, 7 patients were excellent, 22 patients were good and 3 patients were poor. Regarding complications 2 patients developed local recurrence, 2 patients had superficial infection. Infected cases were treated by systemic antibiotic treatment. All patients had dexterity of the hand and elbow. Regarding shoulder abduction and forward flexion, 7 patients whose deltoid muscle and axillary nerve could be spared got nearly normal shoulder function but even the patients with loss of deltoid had limited abduction owing to elevation of scapula by shrugging. Elongation of the newly formed shoulder capsule was seen in patients that artificial mesh augmentation was not used. Prolene mesh was used to create a new substitute instead of resected shoulder joint capsule. These patients did not show any elongation at long-term follow-up. All arthroplasties was hemi-type without glenoid reconstruction. Hemiarthroplasty by a modular tumor resection prosthesis system after wide excision of proximal humerus seems to be an effective method of treatment after shoulder malignancies. The main determinant of the function is the status of deltoid axillary nerve and rotator cuff but the patients deprived of structures had a functional upper limb with a good command of the elbow and the hand.