Alkaline hydrolysis of a hardwood lignin (Populus tremuloides) obtained from a steam-aqueous treatment has been studied experimentally. It was found that the main degradation products were catechols, syringols and guaiacols. In the study, the effects of the reaction conditions, such as temperature, reaction time, alkali concentration as well as the lignin origins on the yields of the monomers produced, have been exploited. Under the drastic conditions (350°C for 10 min), about 9% (w/w of initial lignin) catechols could be obtained. At low reaction severity, however, syringol and guaiacol were the predominant products. Alkali concentration also influenced obviously the degradation and demethylation of the lignin and its derivatives.