For over 100 years, the study of amnesia in humans has been limited primarily to subjects with either diencephalic or mesial temporal lobe lesions. However, over the last 30 years, it has been reported that individuals who survived aneurysms of the anterior communicating artery (ACoA) often displayed an amnestic syndrome, despite the fact that diencephalic and mesial temporal structures were intact. This article presents a comprehensive review of the ACoA literature concerning the neurobehavioral and neuroanatomical substrates of what has been termed the "ACoA syndrome". Various theoretical models regarding the neural substrates of amnesia are discussed. Possible directions for future research are outlined.