Meticulous chemical analysis of decaying xylem and linking it to corresponding anatomical modification at the cellular level can improve our understanding of the decay process. The aim of this study was to monitor the histological, chemical, photochemical, and progression of wood degradation by two white-rot fungi at different intervals. Oriental beech wood (Fagus orientalis) blocks were exposed to Pleurotus ostreatus and Trametes versicolor to investigate the degradation capabilities of these two fungi. Light microscopy was used to study the decay patterns in wood. Decayed wood samples were also analyzed to determine lignin, cellulose and sugar contents and also evaluated at two week intervals by FT-IR spectroscopy to study chemical alterations. According to chemical analyses lignin is the most degraded polymer followed by cellulose and hemicelluloses for both white rot fungi. However, both test fungi tended to consume lignin more than cellulose. FT-IR spectra changes for  lignin and carbohydrates in beech wood supported chemical alteration and indicated that both fungi decay wood in a simultaneous pattern.