This chapter describes the properties of tissue-isolated amyloid fibrils through direct chemical analysis, polarization-histochemical studies, different digestions, the chemically induced birefringence reaction (CIBR) and the critical electrolyte concentration (CEC) method. All tissue-isolated amyloid fibrils contain cellular sphingolipids, probably from their intracellular localisation in caveolae and lysosomes. Prion fibrils also contain an inert glucose-only polysaccharide. All other properties are identical to those of the amyloid deposits of the embedded materials. The amyloid fibril has a helical structure, as shown via a polarisation-microscopic analysis and confocal laser-scanning microscopy. Synthetic serum amyloid A (SAA) fibrils also show the phenomenon of birefringence when unstained and with different topo-optical staining reactions. In prion fibrils, carbohydrate, sialic acid and glycosaminoglycan components have been demonstrated. The observation of sulphated glycosaminoglycans is new but could be expected by comparison with other amyloid fibrils. With the potassium permanganate-bisulphite-toluidine blue reaction (PBT), we observe a linearly ordered sugar component with RNA-like characteristics. After RNA A + B digestion, the induced anisotropy of fibril-bound toluidine blue molecules is abolished.