A polymer's thermal conditions during processing in injection molding define the polymer's structure and with this the properties of the final part. Thus prediction of the temperature in the part during processing is of great interest here. One important value for calculating the temperature is the heat transfer coefficient (HTC), or the thermal contact resistance (TCR) between polymer and mold. Because of this, significant work has been done on this topic. This article gives an impression of the importance of HTC in injection molding and an overview over work conducted in measuring and calculating the HTC and the up to now known influences on it.