Distinction between the linkage types 1-->2, 1-->3 and 1-->4 of xylobioses can be achieved on the basis of the unimolecular decomposition spectra of the oxonium ions of the per-O-acetylated methyl glycosides. The spectra of the oxonium ions of various unbranched xylotri-, tetra- and pentaoses allow determination of the linkage position between the xylose residues. This indicates that in unbranched peracetylated xylo-oligosaccharides the linkage between the xylose residues at the non-reducing end can be determined.