GM2 ganglioside, beta-GalNAc-(1-4)-[alpha-Neu5Ac-(2-3)-]beta-Gal-(1-4)-beta-Glc-(1-1)-Cer, is the main ganglioside in the brain of Tay-Sachs patients. In this work, GM2 ganglioside was extracted from a Variant B Tay-Sachs human brain, purified to homogeneity of the oligosaccharide moiety by silica gel chromatography. It was further fractionated for the first time into the molecular species differing in the ceramide structures by reverse-phase flash chromatography. The GM2 ganglioside species were characterized by gas-chromatography, nuclear magnetic resonance spectroscopy, and mass spectrometry. The major GM2 species contained the ceramides with d18:1-18:0 (40.5% of the total GM2 species), d20:1-18:0 (31%) and d18:1-20:0 (12%). We also found minor GM2 species with the ceramides with d18:1-24:1 (4%), d18:1-22:0 (2%) and d18:2-24:1 (1%), which have not been reported previously.