Desorption chemical ionization-pyrolysis-mass spectrometry (via a heated platinum filament) of polysaccharides with ammonia reagent gas yields ions which appear to be ammonium adducts of anhydrohexoses ( m/z 180) and of anhydro-disaccharides (i.e., m/z 342), apparently related to products of known pyrolytic fragments of polyhexoses and containing stereochemical and linkage features of the polymeric structure. These product ions were investigated by collision induced dissociation reactions in a tandem mass spectrometer. Samples of the polysaccharides starch, laminarin, dextran and agar, and of related anhydrosugar standards were examined. Preliminary results indicate that desorption chemical ionization-pyrolysis-tandem mass spectrometry provides both linkage information and differentiation among monosaccharide stereoisomers of the carbohydrates examined.