Two patients had granulomatous angiitis of the CNS. The typical vasculitis involved the small branches of the cerebral arteries in both patients and resulted in thrombosis of the left middle cerebral artery in one. EM demonstrated structures resembling Mycoplasma organisms. These were present in small numbers in the wall and in the granulomatous reaction within the lumen. Giant cells were observed containing particles suggestive of Mycoplasma within the perinuclear cisternae. Virus-like particles were not observed.