We have studied the regional distribution of glycoasparagine storage material in the brain in aspartylglycosaminuria, a condition characterized by inherited deficiency of lysosomal N-aspartyl-beta-N-acetylglucosamine amidohydrolase. Gaschromatographic measurements of the main accumulating glycoprotein-derived metabolite, N-acetylglucosaminyl-asparagine (GlcNAc-Asn), in 12 defined cerebral areas showed that GlcNAc-Asn is rather evenly distributed in the brain. The mean concentrations ranged from 0.454 mg/g wet tissue (corpus callosum) to 0.0610 mg/g (pons). The GlcNAc-Asn concentrations tended to be higher in grey matter areas than in white matter areas. GlcNAc-Asn was identified in the isolated neuronal fraction, but not in the myelin fraction, by mass-fragmentographic techniques. Electron-microscopic reexamination of a brain biopsy specimen revealed, in addition to the abundant presence of storage lysosomes in the neuronal perikarya, numerous cytoplasmic inclusions in brain capillary endothelial cells and pericytes as well as in occasional macrophages. The results indicate that the glycoasparagine storage material is not limited to expected cortical areas in aspartylglycosaminuria, but is distributed in a rather constant fashion in all cerebral grey and white matter areas studied.