The crystallization of poly(ethylene terephthalate) has been followed in real time by measuring the dielectric complex permittivity. The measurements have been discussed by assuming the contribution to the dielectric losses of two types of amorphous phases : amorphous regions filling the interspherulitic space and amorphous regions located between crystalline lamellae within the spherulites. The deviation of the measurements from the calculated values assuming a simple two-phase model has been interpreted as being due to changes in the nature of the amorphous regions as crystallization proceeds. A phenomenological description of the experiments in terms of the Havriliak-Negami description permits the changes of the relaxation time distribution functions upon crystallization to be followed. The evolution with crystallization time of the derived dipole moment time correlation functions are discussed in the light of different models.