Human brain lipofuscin isolate was studied for its purity and physical and chemical properties. Purification of the impure material was achieved by gel permeation chromatography using Sephadex LH-20 and BioBeads S-X1 gels. The purified lipofuscin polymer represented ca. 12% of the starting material with the rest of the material being various mixed lipids. The mol wt of the purified lipofuscin was determined to be between 6000–7000 daltons. IR, UV-visible, NMR, and fluorometric spectra were obtained, all indicating the fundamentally lipid nature of lipofuscin. The NMR spectrum strongly resembled that of a typical long chain fatty acid. Numbers of fatty acids and several amino acids were present as a portion of the lipofuscin structure. The results obtained suggested that the brain lipofuscin employed in the present study consisted mainly of polymeric lipid and phospholipid structures along with amino acids either bound to the lipids or as included proteins.