We encountered a case of aspergillus granuloma in the cavernous sinus originating in the left sphenoid sinus. The patient was a 56-year-old woman who complained of visual loss and cavernous sinus syndrome on the left side. Hematological data were within normal limits. Bone CT showed evidence of bone destruction in the roof of the left sphenoid sinus. MR images with gadolinium demonstrated an enhanced heterogeneous mass extending from the left sphenoid sinus to the cavernous sinus and the orbital apex. Angiography showed occlusion of the left internal carotid artery. Dexamethasone was administered intravenously every day, because the patient was diagnosed as having Tolosa-Hunt syndrome (THS). However, dexamethasone was not effective. We carried out a biopsy of the mass from the sphenoid sinus, and findings showed aspergillosis. On the 19th day after initiation of fluconazole treatment, the patient lapsed into unconsciousness and presented left hemiparesis. T2-weighted MR images showed high intensity areas in the pons and the thalamus. The patient died two days later. An autopsy revealed edema and many infarctions throughout the brain. The cavernous sinus had been replaced completely with aspergillus granuloma. Furthermore, numerous hyphae of aspergillus had adhered to the inside of the basilar artery, and caused occlusions of arteries around the brain. This case indicated the difficulty of diagnosis of THS and the hazard of over-application of steroids. In this paper, we describe the clinical and pathological behavior of aspergillosis in the cavernous sinus.