Chemical and anatomical properties of tumorous and normal wood of Quercus robur L. subsp. robur were compared. Tumorous growth appeared as a result of topping stress. Orientation of cells was severely disrupted in the affected wood. In cross section, aspects of cells changed abruptly from transverse to longitudinal, and in tangential section all wood elements appeared to turn around each other like a fingerprint. Vessel elements and fibres of affected wood were shorter than those of healthy wood. The vessels of affected wood were smaller in diameter especially in the earlywood. On the other hand, multiseriate ray height was shorter than that of normal wood. In addition, perforated ray cells occurred. The ray and axial parenchyma cells of tumorous wood contained dark coloured phenolic compounds. Normal wood had calcium oxalate crystals, while tumorous wood did not. Chemical analyses showed that hemicellulose content and solubility rates in 1% NaOH, cold water, hot water, and alcohol- benzene were higher than those of normal wood. Cellulose and ash contents of tumorous wood were slightly lower than in normal wood. In addition, air-dry specific gravity of tumorous wood was higher than that of normal wood.