Woods were degraded by analytical pyrolysis at 450-degrees-C. The degradation products were separated by gas chromatography and the polysaccharide derived degradation products were characterized by mass spectrometry using electron impact (EI) and chemical ionization (CI). The complete (EI) mass spectra and structural formula of 104 polysaccharide derived products are presented. The mass spectral recognition of anhydrosugars and the presence of structure isomers from dihydro-methyl-furanones in the product mixture is discussed.