The study of the degradation carried out by microorganisms on plant cell walls poses several problems in the analysis of the degraded solid materials. In this article this analytical problem has been studied by solid-state, high-resolution, carbon-13 cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) and Fourier-transformed infrared (FT-IR) spectroscopy. These two nondestructive techniques proved to be able to give insights into the modifications at a molecular level that the cell wall components undergo during attack by Basidiomycetes fungi. Spruce (Pinus sylvestris) and beech wood samples (Fagus sylvatica) were exposed for 6 weeks to the activity of brown-rot (Coniophora puteana) and white-rot (Coriolus versicolor) fungi. Brown-rot fungi appeared preferentially to degrade the polysaccharides, leaving a modified lignin network, whereas white-rot fungi were able to degrade extensively both the polysaccharides and the lignin. A quantitative approach based on integration of CP/MAS NMR spectra showed that spruce lignin was degraded to 77% of its weight by brown-rot, and to 39% by white-rot fungi.