Fourier transformed infra-red (FTIR) was evaluated as an analytical tool for monitoring wood biodegradation. A sample set containing typical soft (Pinus radiata) and hardwood (Eucalyptus globulus) decayed by six white- and two brown-rot fungi was prepared. Biodegradation times from 30 days to 1 year provided samples that suffered weight losses varying from 0.4% to 36% for pine wood and 1.7% to 42% for eucalyptus wood. Decayed samples were characterized by conventional wet chemical analysis and by diffuse reflectance FTIR (DRIFT) spectroscopy. Multivariate analysis was applied to correlate chemical composition in wood samples with the FTIR spectral data. Partial least squares (PLS) models were able to predict the major wood components' concentrations at the 99% confidence level presenting r(2) values higher than 0.86 in most cases. Models for P. radiata were more precise than for E. globulus.