Between 1976 and 1991, we determined that 19 patients harboring bilateral supratentorial aneurysms should be approached in a single sitting through a unilateral pterional craniotomy. Using microsurgical techniques, the Sylvian cistern was opened widely to expose the aneurysms located ipsilateral to the craniotomy. These aneurysms were clipped in the usual fashion. Following clipping, a tunnel was developed over the contralateral anterior cerebral artery and over or under the contralateral optic nerve allowing access to the opposite carotid and middle cerebral arteries. The contralateral nonruptured aneurysms were clipped in a routine fashion. We were able to clip or wrap with muscle all bilateral aneurysms in 15 cases, and we have concluded that this approach can be safely employed in selected patients with bilateral supratentorial aneurysms, and thus a second craniotomy can be avoided.