An aneurysm of a persistent primitive hypoglossal artery (PHA) particularly at its junction with the basilar artery, often poses therapeutic problems. This is attributable not only to the size and location of the aneurysm but also to the fact that the persistent PHA is functionally the single artery providing blood in posterior circulation. We report a 31-year-old man with a large aneurysm of the persistent PHA at its junction with the basilar artery and review the existing literature. We clipped the broad neck of the aneurysm through a lateral suboccipital craniectomy; however, the patient suffered a second episode of subarachnoid hemorrhage. Angiography disclosed a slipped clip incompletely obstructing the persistent PHA. He received no further treatment for the aneurysm because of his deteriorating condition. Direct surgical treatment, although it failed to obliterate the aneurysm neck in our patient, should be recommended for a persistent PHA aneurysm.