We performed MR (magnetic resonance) brain imaging on 24 patients with a systemic vasculitis. MRI proved to be a sensitive method for detecting brain lesions (clinically silent or manifest) in these patients. The most frequent abnormalities were periventricular lesions seen in 12 cases. Such changes are not specific for vascular disease, and are often seen in multiple sclerosis. However, additional changes were commonly seen which suggested the correct diagnosis.