Lignin as a part of wood biomass has been proposed to be an alternative source of chemical compounds for industrial applications. The degradation of lignin was studied in near and supercritical water at temperatures 623 and 673 K using a batch type reactor. The effects of temperature and reaction time were combined into a single severity parameter that was used to monitor the degradation of lignin to liquid fraction. With an increase in the reaction time at the same conditions, higher molecular weight fractions decreased and the amount of lower molecular weight fractions increased. The chemical species in liquid products and solid residues (char) were analyzed using high performance liquid chromatography with a Jasco MD-2010 Plus and Fourier transform infrared spectrophotometer, respectively. The main products in methanol soluble fraction were catechol (28.37 wt%), phenol (7.53 wt%), m,p-cresol (7.87 wt%) and o-cresol (3.80 wt%). Based on the experimental results, a reaction mechanism for the degradation of lignin was proposed. Next, optimum-operating conditions for high yields of valuable chemicals could be explored. (C) 2007 Elsevier B.V. All rights reserved.