Postmortem neuropathological findings in a patient with biopsy-proved familial Gerstmann-Sträussler-Scheinker disease of eight years' duration included severe spongy change in the neocortex, extensive and often large amyloid deposits throughout the cerebral hemispheres and cerebellum, and severe astrocytic gliosis throughout all areas of gray and white matter within the brain. The degree of cortical spongy change was much greater than that in relatives who died with a similar clinical history, indicating the phenotypic heterogeneity in this familial disorder.