Brain sections from cases of human Creutzfeldt-Jakob disease, Gerstmann-Sträussler syndrome, kuru, and hamster scrapie containing amyloid were examined for the presence of sulfated glycosaminoglycans (GAGs), the anionic component of proteoglycans, using the sulfated Alcian blue method and Alcian blue technique with 0.3 M and 0.7 M magnesium chloride. These studies suggest that sulfated glycosaminoglycans are part of the CNS amyloid plaques in each of the above human prion disorders as well as in experimental scrapie. All the amyloid plaques stained positively with Alcian blue at 0.3 M, and less so at 0.7 M magnesium chloride indicating the presence of sulfated GAGs. Therefore, the amyloid plaques of prion diseases possess similar histochemical features to those found in Alzheimer's disease.