A case of cervico-arterial fibromuscular dysplasia (FMD) associated with an aneurysm of middle cerebral artery was reported in a women aged 54. On December 12, 1983, she was admitted to our hospital, who had been diagnosed as head injury (cerebral concussion) and a cerebral aneurysm. On admission, her general condition was favorable, her conscious was clear and neurological examination was normal. The four vessels cerebral angiograms showed right M1M2 aneurysm and FMD which was characterized as typical changes of form "string of beads" in the extracranial internal carotid and vertebral arteries of both sides. Clipping of aneurysm was performed and favorable post-surgical progress was observed. FMD of the cervico-cephalic arteries has been seen rarely in Japanese, but the detection frequency of FMD from cerebral angiography is 0.3-0.9% and the frequency of complication with aneurysm is high at 13-51% on literature. The histologic similarities between intracranial aneurysms and the aneurysmal dilatations of FMD are the absence of the muscular media and a defective interval elastic lamella. This paper suggested strong relationship between FMD and cerebral aneurysm.