Cerebral aneurysms are the predominant cause of spontaneous subarachnoid hemorrhage (SAH). However, if an aneurismal cause has been excluded, there remains but a short list of meningiomas or metastatic lesions as possible causes. This article details a case of neoplasm that presented exclusively with SAH. A 31-year-old male presented with a SAH with normal cerebral angiography. The initial magnetic resonance image (MRI) revealed a lesion in the left uncus thought to be recovering hemorrhage. Subsequent MRI, however revealed the mass to be expanding. A neuroendoscopical biopsy of the lesion established a diagnosis of glioblastoma. An affirmation is made that patients experiencing "angiographically-negative" SAH should undergo MRI, occasionally on a serial basis, to exclude other etiologies for hemorrhage, including neoplasma.