Ganglioside fractions were isolated from brains of man, cow, horse, pig, sheep, cat, rabbit, rat, chicken and codfish. The acylneuraminic acid residues, liberated from these gangliosides by treatment with dilute aqueous acid or neuraminidase, were analysed by the thin-layer chromatography and combined gas-liquid chromatography/mass spectrometry. Small amounts (up to 20%) of 9-O-acetyl-N-acetylneuraminic acid, and in bovine and porcine brain gangliosides also traces of N-glycoloylneuraminic acid, were found in addition to N-acetylneuraminic acid.