A 27-year-old woman is described who suffered an acute left hemiplegia at the age of three years and 20 years later she noted the onset of unilateral left limb dystonic movements. Her cranial CT scan showed an area of low density, consistent with longstanding infarction, in the right lentiform nucleus. Cerebral angiography demonstrated aneurysmal dilatation of the terminal portion of the right internal carotid artery, minor irregularity of the lenticulostriate branches of the right middle cerebral artery (suggestive of Moya Moya disease) and occlusion of the right anterior cerebral artery. The dystonic movements improved with levodopa therapy. Clinico-radiological correlation in this case supports recent evidence for a disruption of pathways between the caudate nucleus, lentiform nucleus and thalamus in the pathophysiology of hemidystonia.