A prototype organosolv lignin was hydrocracked at temperatures of 370–410°C in the presence of tetralin, a hydrogen donor solvent. The effects of temperature and time were combined into a single severity parameter that was used to monitor the conversion of lignin to liquid and gaseous products as well as the distribution of important liquid products. A nickel-tungsten catalyst was used in most of this work. At the highest severity of treatment, conversion of lignin did not exceed 50 wt%. The high yields of either reactor residue (at low severity) or residual lignin (at high severity) suggest that the reaction conditions used were not sufficient to degrade the lignin to liquid and gaseous products. The distribution of liquid monomeric compounds was too wide and their yields were too low to warrant complete identification and quantification by capillary gas chromatography. However, from the relative abundance of representative peaks in the chromatograms of acetylated compounds in the dichloromethane-solubles, syringols and guaiacols predominated at low severities of reaction. At high treatment severities, demethoxylated compounds (phenols, catechols and their methyl and ethyl derivatives) were the major liquid products. The addition of nickel-tungsten heterogeneous catalysts with either low (3 wt%) or high (60 wt%) Ni content only marginally improved the yields of monomeric phenolic compounds. However, much higher gas yields were produced when using the 60 wt% Ni catalyst.