• A 29-year-old woman with a five-year history of systemic lupus erythematosus was seen after having had a grand mal convulsion, her first manifestation of a seizure disorder. A lumbar puncture revealed the presence of subarachnoid blood, and angiography demonstrated a fusiform aneurysm of the left posterior communicating artery. The patient's neurological status deteriorated despite the use of corticosteroids in high dosage, and she died three weeks after admission. Necropsy disclosed focal transmural angiitis at the site of the ruptured aneurysm. This report describes a radiographically and pathologically confirmed case of CNS lupus producing focal angiitis of a medium-sized cerebral vessel with secondary aneurysm formation.