A 35-year-old male with a sudden onset of severe vertigo and vomiting had a fusiform aneurysm of the distal portion of the left posterior inferior cerebellar artery. The symptoms were caused by cerebellar infarction probably due to an embolism from the aneurysm. The aneurysm was excised and the artery reconstructed by end-to-end anastomosis with an excellent outcome. Histological examinations showed mural thrombus but no wall dissection.