The objectives of this study were to investigate the effects of temperature and relative humidity on the sorption characteristics and the drying rate of woody biomass, and to develop a sorption isotherm model. Experiments using Trembling Aspen (Populus tremuloides) as materials were conducted in a controlled environment chamber. Results showed that low temperature and high relative humidity of ambient air led to higher equilibrium moisture content (EMC) for both desorption and adsorption processes. At higher temperature, the EMC was reached over a shorter drying time indicating a higher sorption rate; relative humidity was also positively correlated with the adsorption rate. The Modified Oswin model that relates equilibrium relative humidity to temperature and EMC was found to provide the best fit to the experimental data. The trend of drying rate constant versus temperature followed the Arrhenius equation, and Page's model was appropriate for predicting the drying characteristics of Aspen. (C) 2013 Elsevier Ltd. All rights reserved.