The sugar fraction of alpha-1 acid glycoprotein (AGP) was studied using porous graphitized carbon (PGC) chromatography coupled to mass spectrometry. Electrospray ionization provides efficient control over fragmentation; at low collision energy only molecular species were observed, allowing accurate oligosaccharide profiling. PGC chromatography was useful separating 18 sugars differing in monosaccharide composition. Most of these were separated into several isomeric forms; altogether 49 different oligosaccharides were found in AGP.