A rare type of fibromuscular dysplasia of the common carotid artery, in the form of a septum, was observed in a patient suffering from recurrent cerebral infarctions. Angiography demonstrated growth of the lesion and documented the presence of an intraluminal thrombus attached to it. Comparison with reported cases of the more common "string of beads" lesion of fibromuscular dysplasia suggests that the risk for development of ischemic neurological problems is higher for this type of fibromuscular lesion. Surgical correction is recommended, especially for symptomatic patients.