A saccular aneurysm of the posterior inferior cerebellar artery lying in the fourth ventricle and an arteriovenous malformation in the cerebellum fed by the same artery are reported. Clipping of the neck of the aneurysm and total removal of the arteriovenous malformation were performed successfully during one stage. Review of the pertinent literature indicates that the aneurysm of the posterior inferior cerebellar artery originates from the peripheral portion of the artery when associated with arteriovenous malformation. The treatment is often surgical with good results in more than 80% of cases. A one-stage operation is the method of choice. Embolization is not without risk and can be attempted when the PICA's course allows easy catheterization.