The study of polymer dynamics was historically one of the first applications of fast field-cycling (FFC) relaxometry owing to the extremely broad range of frequencies of reorientations in the melt, solution and solid state. Research on polymer melts has turned out to be the most interesting topic and has led to the critical investigation of dynamic models, some of which were developed even during the lifetime of FFC as a method. Even today, many questions, particularly about the slow dynamics of chain molecules, remain hotly debated, and the field has branched out towards more complex polymers, multicomponent systems and confinements. These developments have required, and also triggered, developments in the hardware and software of FFC technology – for instance, the move towards ultra-low magnetic fields was partly motivated by the quest to investigate polymer dynamics in the kilohertz range and below, and to distinguish intra- and intermolecular correlations from each other. This chapter summarizes the state of the art of polymer melt studies and discusses selected applications beyond this field.