A 72-year-old woman developed difficulty reading, driving, and playing dominoes. Ophthalmologic examination revealed a homonymous hemianopia, but brain MRI showed no abnormality to explain the visual field defect. Neuropsychiatric testing demonstrated severely impaired visual processing (simultagnosia, visual agnosia, visuospatial difficulty). Positron emission tomography revealed hypometabolism of both parietal and occipital lobes consistent with posterior cortical atrophy or the visual variant of Alzheimer disease. Functional neuroimaging should be considered in the setting of a normal MRI among patients with signs and symptoms of the visual variant Alzheimer disease.