We studied 11 patients with amnesia and personality change after surgical repair of ruptured anterior communicating artery (ACoA) aneurysm. CT and clinical evidence suggested that infarction in the territory of the ACoA was responsible for amnesia and personality change. The medial septa1 nuclei, the paraventricular nucleus of the anterior hypothalamus, and the medial forebrain bundle are the primary areas of potential interest in these cases. Gross infarction in the frontal lobes is not a requirement for the syndrome.