A case of intracranial bilateral vertebral artery (VA) dissection presenting with ischemic symptoms which following unilateral dissection is presented. A 42-year-old male with an occipital headache was pointed out right vertebral artery stenosis with magnetic resonance (MR) angiography 8 day before admission. He admitted to our hospital complaining of severe vertigo and tinnitus. MR images and cerebral angiograms revealed bilateral VA dissection with infarcts in light lower surface of cerebellum perfused by posterior inferior cerebellar artery and right hypothalamus. Conservative therapy was adopted and serial MR angiography was performed. His symptoms were improved gradually and MR angiograms obtained 2 months later revealed improvement of bilateral VA stenosis. It is generally accepted that VA dissection presenting ischemic symptoms has good outcome by conservative therapy only. However, its pathological process of progression is still unknown. Based on the serial MR findings, we discuss the mechanisms of bilateral VA dissection. In this case, we consider that unilateral VA dissection extended to contralateral vertebral artery through the vertebrobasilar junction. Frequent MR angiography in acute phase could be of great use for monitoring the progression of dissection.