The clinical, radiologic, and histologic features of 22 cases of Paget sarcoma were reviewed to determine in which patients with Paget disease these tumors are most likely to develop and what radiologic findings suggest the diagnosis. Clinical findings at presentation included pain and/or a mass (11 patients), pathologic fracture (seven), and neurologic symptoms (four). Survival time in 20 patients ranged from 5 days to 2.5 years. Two patients were lost to follow-up: one at 2 years and one at 8 years. There were 16 high-grade osteosarcomas, three chondrosarcomas, two fibrosarcomas, and one malignant fibrous histiocytoma. The most common site was the femur. Tumors also were observed in unusual sites. In one case of multifocal osteosarcoma, the tumor involved only pagetic bone. In 15 patients, Paget disease was polyostotic, clinically significant, and had been documented previously. In four patients, a sarcoma developed near the site of a fracture that had occurred between 2 months and 15 years previously. All cases showed radiologic evidence of a destructive lesion; other findings included a mass and evidence of tumor mineralization. Periosteal reaction was not observed. All but one tumor developed in a site of osteoblastic or mixed osteoblastic and lytic Paget disease. Our results suggest that sarcomas can develop in any part of any bone affected by Paget disease but are more likely to occur with advanced disease and to present with a destructive lesion without periosteal reaction.