Sound (undecayed control) and fungally-pretreated wood samples were submitted to organosolv delignification. The cooking liquor used was methanol/water (78:22 v/v) containing CaCl2 and MgSO4 each at a concentration of 25 mmol dm(-3), The cooking process was performed at 180 degrees C for reaction times varying from 5 to 100 min. Despite some differences in. the lignin removal pattern, pseudo-first order kinetic models permitted a prediction of delignification rate constants for all experiments, All biodegraded samples provided higher delignification rate constants than the undecayed control (2.0 x 10(-2)min(-1) for the undecayed control and, for example, 14.2 x 10(-2)min(-1) for the sample decayed by Trametes versicolor for 2.5 months), Biodegraded samples also presented significantly increased xylan removal rates. The type of biodegradation affected the behavior of wood samples under organosolv pulping, The highest delignification and xylan removal rate constants were observed in the sample decayed by T versicolor for 2.5 months (17% weight loss). However, high delignification and xylan removal rate constants were also observed in the sample decayed by Punctularia artropurpascens for only 0.5 months (1.2% weight loss). Data obtained from a single fungal species pretreatment or data from all fungal pretreatments indicated that there is no clear correlation between the delignification constants and the wood weight or component losses. This lack of correlation suggested that the structure of residual polymers in decayed wood affects the delignification process in the organosolv pulping more than the removal extent of each individual component.