The rich behavior of thermoplastic polyurethanes (TPUs) undergoing phase transition is investigated by means of combined theological and DSC techniques. In particular, the kinetics of micro-phase transition of a commercial TPU are followed under both isothermal conditions (crystallization from the melt), and constant temperature rate heating ramps (melting). In rheological tests, the time evolution of the storage modulus is monitored by using a strain rate-controlled rheometer. The rheological results are compared with those obtained by more traditional calorimetric techniques (DSC) under the same thermal histories. It is shown that rheological measurements can give additional (and, in some cases, more accurate) information than that obtained from the more classical thermal analysis. (C) 2004 Society of Plastics Engineers.