N- and O-linked glycosylation are some of the most common, abundant, and biologically important posttranslational modifications of proteins, yet they are also some of the most difficult to study. The dominant analytical platform for the study of glycosylation is mass spectrometry, yet this platform on its own is incomplete, because it cannot elucidate glycan topology and linkage stereochemistry. This project will advance the use of mass spectrometry for glycan structure determination, especially for the case of O-linked glycans, by studying the ion propensities of various structural motifs in multi-stage ion trap mass spectrometry, and by building new software for structure inference from such mass spectra.