A case of osteogenic sarcoma of the skull in a patient with a long-standing Paget's disease is reported. Osteogenic sarcoma arising within the skull is rare in Paget's disease, although the recent literature emphasizes that it is more common than was realized previously. Intraparenchymal brain invasion, which is rare and present usually only as a preterminal event, was found in this patient who presented initially with minimal neurological findings. Rapid neurological deterioration in this patient was due to macroscopic hemorrhage into tumor. Although microscopic hemorrhage is characteristic of this tumor, gross hemorrhage into osteosarcoma of the skull as a cause of sudden neurological deterioration has not been reported previously. Radical resection is the treatment of choice, although the prognosis for this tumor remains dismal.