Migraineurs with frequent aura (>or=1 per month) are at a 12-fold increased risk of posterior circulation infarctions. Although the mechanism is unclear, these lesions are located in the arterial borderzone of the cerebellum. This case illustrates, for the first time, crossed cerebellar diaschisis in a patient with migraine with prolonged aura, and raises the possibility that hypoperfusion may be responsible in part for the development of these lesions.