Twenty-two neutral O-linked oligosaccharides ranging from monosaccharides to octasaccharides were identified in bovine submaxillary-gland-mucin glycoprotein by a combination of liquid secondary-ion mass spectrometry, methylation analysis and 1H-NMR. Only five of these have been previously detected in bovine submaxillary-gland mucin although several have been described from other sources of mucin. The structures include short linear sequences 3-linked to N-acetylgalactosaminitol (GalNAcol) and branched structures based on either a GlcNAc(beta 1-6) [Gal(beta 1-3)]GalNAcol or GlcNAc(beta 1-6)[GlcNAc(beta 1-3)]GalNAcol core region. Oligosaccharides not previously characterised from any source were the disaccharide GalNAc alpha 1-6GalNAcol (GalNAc, N-acetylgalactosamine and the hexasaccharide GlcNAc(beta 1-6) [GalNAc(alpha 1-3)( Fuc (alpha 1-2)]Gal(beta 1-4)GlcNAc(beta 1-3)]GalNAcol (Fuc, L-fucose). Oligosaccharides of the blood-group-A type have not been detected previously in bovine submaxillary-gland mucin although their occurrence on bovine gastric-mucosal glycoproteins has been established by classical immunochemical studies.