Granulomatous angiitis is an uncommon necrotising vasculitis of unknown cause restricted to vessels of the central nervous system. Five tissue-proven cases emphasise the protean manifestations of this disease and the difficulties encountered in reaching a diagnosis. One patient presented with a temporoparietal mass, the second, a progressive dementia, the third suggested herpes simplex encephalitis, the fourth mimicked multi-infarct state; and the fifth presented with a cerebellar mass lesion. In four cases with CSF examination, protein was elevated (81-193 gm/l) and three patients had mononuclear pleocytosis (12-800 WBC/mm3). Cerebral arteriogram suggested vasculitis in only one of four cases. Diagnosis was made by brain biopsy in three cases and all three were treated successfully. The diagnosis in the two other cases was made at postmortem examination.