A 55-year-old patient experienced a pure amnestic syndrome of insidious onset that worsened progressively. Subsequently, her memory disorder stabilized and remained her only cognitive impairment for several years. She ultimately developed more widespread cognitive decline and terminal dementia. Postmortem examination 18 years after the onset revealed numerous senile plaques and neurofibrillary tangles consistent with Alzheimer's disease. A permanent pure amnestic syndrome of insidious onset may represent a further type of focal cerebral degeneration.