This paper describes an 11-month-old male who died of Sandhoff disease. Diagnosis was based on detection of cherry red spots and total deficiency of hexosaminidase A and B activities. Sections of the brain revealed swollen neuronal cells and their degeneration and disappearance, leaving a distorted cortical architecture. Ultrastructurally, numerous inclusions showing concentric lamellar or stacked lamellar profiles were found in ballooned neuronal cells, astrocytes and histiocytes. The parafoveal retina in the region of the cherry red spot contained ballooned ganglion and amacrine cells filled with PAS and LFB positive granules. Electron microscopically, these cells showed a greater accumulation of inclusions with stacked lamellar profiles, than the concentric lamellar ones, of classically membranous cytoplasmic bodies (MCB). Hepatocytes and Kupffer cells and epithelial cells of renal glomeruli contained pleomorphic inclusions. Biochemical analysis by thin-layer chromatography of lipid extracts from the cerebral cortex showed a marked increment of the GM2 fraction, without an increase in globoside.