Isolated oculomotor paralysis was produced by an unsuspected saccular basilar aneurysm in one case and fusiform basilar aneurysm in another. The chronicity of symptoms and lack of pain were misleading features. The saccular basilar aneurysm, which has an untreated mortality of 50% to 80%, was visualized best with selective angiography and successfully clipped intracranially. The fusiform basilar aneurysm, part of a diffuse atherosclerotic ectasia of all basal intracranial arteries, indented and displaced the upper brain stem. A common ophthalmologic sign of posterior communicating aneurysms, oculomotor paralysis has not been documented frequently with basilar aneurysms.