Kinetic models were developed to give an interpretation of several phenomena involved in wood fractionation. Experimental data (obtained in wood treatments at normal boiling temperature with 95% acetic acid solutions containing 0.05-0.2% HCl), were used to develop kinetic equations for. (i) solid residue yield, (ii) solid residue composition (including lignin, cellulose and hemicelluloses) and (iii) reaction products from hemicelluloses (including sugars and furfural). By means of empirical equations the kinetic parameters were correlated with the catalyst concentration used in the various experiments, leading to generalized models useful for technical and economic evaluation of the studied process.