Amyloid fibrils isolated from two patients, one with inherited systemic amyloidosis and lattice corneal dystrophy, and the other with secondary amyloidosis due to chronic glomerulonephritis, were studied using immunologic, electrophoretic and chromatographic techniques. Amino acid hydrolysates of both amyloid types showed a high proportion of acidic and aliphatic amino acid residues but were non-identical in the overall amino acid composition. The preparations also contained 12--16% lipids. Guanidine hydrochloride denaturated amyloid fibrils of both types were resolved into four fractions in Sepharose 6B chromatography with molecular weights of ca. 160 000, 45 000, 20 000 and 8 000. The 160 000 mol. wt. fraction predominated in the chromatograms of inherited amyloid protein and was further resolved into two main fractions of 17 000 and 15 000 mol. wt. in sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. None of these fractions from inherited amyloid protein showed immunologic identity with tissue-derived amyloid protein A (AA) whereas all four fractions from secondary amyloid reacted against anti-AA antiserum. The three major Sepharose 6B fractions of secondary amyloid fibrils were resolved into a 25 000 mol. wt. fraction in SDS-polyacrylamide gel electrophoresis without urea but into a 12 000 mol. wt. fraction in gels containing 8M urea after more drastic dissolving conditions of the fibrils.