Glycogenosis Type VIII, characterized ultrastructurally by an accumulation of rosettes (alpha-particles) of glycogen in the central nervous system, is an extremely rare condition; only two sporadic cases are on record. The first complete autopsy on a patient with cerebral alpha-particle glycogenosis, a 20-year-old American-Indian female, is the subject of this report. The case was clinically unique because of long survival and presumable familial incidence. The gross pathology was characterized by severe brain atrophy but preserved thickness of the cortical mantle. Vacuolation of the neuropil was the main histological abnormality and was most extensive in the striatum and less so in the cerebral cortex and some brain stem nuclei. Biochemical analysis showed glycogen levels elevated fiftyfold in the striatum and eightfold in the cerebral cortex in comparison with control tissue. Ultrastructural observations and evidence obtained from the Golgi method suggest that the distal axon was the principal site of storage. Two prominent additional abnormalities, spheroids, not previously observed in this disease, and massive accumulation of lipofuscin, were probably both related to the prolonged course of illness. The viscera, including the liver were morphologically free of storage.