Two cases of glioblastoma multiforme (GBM) diffusely metastatic to bone marrow are presented; both patients developed back pain, thrombocytopenia, and hemorrhagic diatheses from their diffuse bony disease. In one patient the intracranial and extracranial symptoms were synchronous in their presentation. Both patients had known dural involvement by GBM at the time of craniotomy and dural venous invasion microscopically. Tumor infiltration of dura and dural vessels is a significant mechanism for extracranial spread and should be noted by surgical pathologists in their reports if it is found. Although cases of metastatic GBM have been uncommon in the past, especially without antecedent surgery or ventriculoperitoneal shunt placement, better control of local disease may enhance the possibility of extracranial spread in the future from GBM. The finding of dural invasion by GBM either at surgery or microscopically should prompt oncologists to initiate at least a limited metastatic work-up for this subset of GBM patients.