Fibromuscular dysplasiais an uncommon condition of idiopathic, non-inflammatory and non-atherosclerotic disease of the musculature of arterial walls. The disease is rare, but it commonly affects young and middle aged women. Isolated intracranial cerebral fibromuscular dysplasia is extremely rare because cerebral fibromuscular dysplasia usually affects extracranial vessels. A 20-year-old woman was admitted with light hemiplegia and global aphasia. Brain MRI and MRA demonstrated acute left middle cerebral artery territory infarction with a multifocal stenosis and dilatation of the left middle cerebra artery and left internal carotid. The characteristic conventional cerebral angiographic findings demonstrated a typical string-of-beads appearance in the left distal internal carotid artery and proxiaml portion of the left middle cerebral artery, which suggested a medial type fibromuscular dysplasia. We report a case of isolated intracranial fibromuscular dysplasia with left middle cerebral artery territory infarction. Fibromuscular dysplasia should he considered as a stroke risk factors in children and young adults, especially in patients with no known cardiovascular risk factors.