Aneurysm of the vertebrobasilar system is not a rare lesion but constituting 5-10% of all intracranial aneurysms. Aneurysm at the peripheral part of the anterior inferior cerebellar artery (AICA), however, is rare and only 20 cases have been reported previously. In this report, two cases of aneurysm arising at the junction between the AICA and internal auditory artery and extending into the internal auditory meatus are reported. The first patient was a 51-year-old male who was admitted because of sudden onset of dizziness, rt. tinnitus and deafness. Left vertebral angiograms demonstrated an AVM in the rt. cerebellar hemisphere and two aneurysms on the feeding arteries, one on the superior cerebellar artery and the other on the meatal loop of the rt. AICA. Removal of the AVM and neck clipping of the aneurysms, which were found unruptured, were performed through the rt. suboccipital approach. The second patient was a 42-year-old female who was admitted because of sudden onset of severe headache and vomiting followed by rt. tinnitus, deafness and double vision. CT scan showed subarachnoid clot mainly located in the rt. cerebellopontine angle. Repeated vertebral angiograms revealed an aneurysm at the meatal loop of the rt. AICA. Complete neck clipping was carried out. The clinical features of the aneurysms of this location can be divided into three subgroups according to the characters of onset: sudden onset with subarachnoid hemorrhage, insidious onset of the VII th, VIII th, nerve palsies by the mass effect of the aneurysm, intermittent episodes of the VIII th nerve disfunction due to the insufficiency of the internal auditory artery.(ABSTRACT TRUNCATED AT 250 WORDS)