The neuropsychological performance of five patients with an anterior communicating artery (ACoA) syndrome (amnesia, confabulation and personality changes) was studied. Neuroimaging techniques revealed a basal forebrain and frontal lobe pathology in all patients. The limbic system appeared intact. There was no evidence for an intellectual deterioration relative to the estimated premorbid IQ in four patients. Regarding attention, all patients showed significant deficits. Visuospatial disabilities could not be observed. On tests of executive functioning, all patients did exhibit severe problems. Every patient displayed a profound amnesic syndrome. A retrograde amnesia could be documented and was characterised by a temporal gradient. Short-term memory appeared normal. Concerning long-term memory, all patients scored out of the normal range on total immediate recall tasks. Four patients showed a normal recognition performance but produced a large number of false alarms. Despite a normal recognition performance, they were impaired in delayed recall tasks. However, one patient showed a full-blown amnesic syndrome, because his delayed recall and recognition of learned items were both depressed. Our results with regard to long-term memory functioning support the hypotheses which assume (1) the existence of recognition superiority and pathological false recognition, and (2) basal forebrain amnesia in ACoA patients.