We report an 82-year-old woman who developed pure topographical disorientation after a cerebral infarction involving the isthmus of the right posterior cingulate gyrus. She lost her way in new environments such as the hospital, but not in old ones such as her own house. She correctly identified familiar or unfamiliar landscapes and buildings by photographs. Her failure to memorize a new route likely resulted from a loss of directional memory over a wide area. We suggest that the right posterior cingulate gyrus contributes to memorizing a new route.