A 73-year-old woman presented with multifocal cerebral dysfunction of 1 month's duration. Cranial CT scanning revealed unusual widespread abnormalities. Brain biopsy showed amyloid angiopathy affecting vessels in the meninges and cerebral cortex, with associated granulomatous angiitis. There was no clinical evidence of extracranial vasculitis. Corticosteroid therapy produced striking clinical and radiological improvement.