A commercial engineering thermoplastic polyurethane (ETPU) resin was investigated by modulated-temperature DSC (MDSC). Use of this recently developed technique provided an accurate measurement of the changes in heat capacity resulting from crystallization and depolymerization processes. The former process was examined in a pseudo-isothermal experiment and the latter in a dynamic one.The ETPU resin investigated in this work is crystallizable but at such a slow rate that no crystalline regions are expected to be formed under normal processing conditions. Significant amounts of crystalline material are not formed until after 150 min at 160 degrees C and the crystallization process is not completely finished even after 700 min. It is shown that the endothermic activity observed upon heating is not a true melting process but is caused by a breakup of the crystalline regions by depolymerization.Heat capacity (C-p) traces obtained from a heat-cool-heat sequence of the amorphous material indicate that no significant irreversible changes to the resin have occurred during the time frame of the experiment. Starting from ca. 175 degrees C, a positive deviation in the linearity of the Cp VS. temperature relationship is observed. It is believed that this deviation is the result of a reversible depolymerization/repolymerization process. Number-average molecular weights, in line with expectations, have been calculated from the observed C-p changes using literature data for polystyrene.