The apparently homogenous N-glycosidically-linked glycans 1, 7, 11 and 14 released by hydrazinolysis from hen ovomucoid were analysed by fast atom bombardment and electron-impact mass spectrometry after reduction and permethylation. The spectra support the primary structures established independently [FEBS Letters (1983) 152, 145-152] using methylation analysis, partial acid hydrolysis and 500 MHz 1H NMR spectroscopy. In addition to the major constituents present in fractions 1, 7, 11 and 14, four minor components not detected by other methods could be characterized with the aid of the mass spectrometry data as: Man2GlcNAcGlcNAc-o1, GlcNAc4Man3GlcNAc-o1, GlcNAc6Man3GlcNAc-o1 and GalGlcNAc6-Man3GlcNAc-o1. Our results show that the physical techniques used provide valuable data on the structure of complex glycans. In addition they can be employed to ascertain the homogeneity of the compounds examined as well as to detect trace amounts of homologs that might not be noticed by other methods.