The permethylated methyl glycoside methyl esters of N-acetyl- and N-glycolyl-neuraminic acids and of N-acetylneuraminic acid 8-acetate have been analyzed by g.1.c.-mass spectrometry. Fragmentation of the neuraminic acid derivatives in electron-impact mass spectrometry has been studied by deuterium labelling. The results were applied in the methylation analysis of neuraminic acids from gangliosides of brain and kidney.