Hemimedullary infarction, which presents Babinski-Nageotte syndrome, has been mainly reported to result from atherosclerotic occlusion of the vertebral artery. A 54-year-old housewife with right nuchal pain developed Wallenberg's syndrome followed by left hemiparesis. Diffusion-weighted magnetic resonance imaging documented fresh infarcts in the right hemimedulla and right dorsal cerebellum. Angiography revealed dissection of the right vertebral artery as a cause of the infarcts. Anterograde progression of the dissection might cause stepwise evolution of her neurological symptoms.