Aneurysms of the internal carotid artery before it reaches the cranial cavity are rare; those arising in the carotid canal (from the petrous segment of the artery) are particularly unusual. A survey of the available literature of the past ten years and of older monographs reveals only three reported instances of aneurysm in the canal.1-4The following account is presented because of the uncommon extension of such an aneurysm, the remarkable symptoms it produced, and the ocular anomaly with which it was associated. In addition, the anatomic and symptomatic response to surgical occlusion of the common carotid artery has thus far been favorable. Report of Case A 34-year-old white male was admitted to Duke University Hospital on July 3, 1961, with a threeday history of left-sided continuous headache and facial numbness. For two years prior to admission he had recurrent bouts of headache. Each was rapid in onset, without