Relationship between thermal-softening properties and deformation appearing after heating and cooling processes with loading was investigated. In the heating process, an obvious decrease in relative relaxation modulus due to thermal-softening of lignin was found at around 60 degrees C. After the cooling process, around 70% of residual deformation was measured. Also, the residual set depended on the maximum temperature reached in the heating process and the unloaded temperature in the cooling process. It was thought that these results suggest that the glass transition of lignin from the rubbery to glassy state is important to fix the deformation. (C) 2010 Elsevier Ltd. All rights reserved.