Porosity, caused mainly by air entrapment, is one of the major casting defects in high pressure die casting and leads to a lower casting quality and poor mechanical properties. Especially hotspots, which occur during solidification, lead to higher grades of porosity due to insufficient feeding. Controlled cooling in these locations would stop the formation of hotspots an increase the casting quality and mechanical properties. The aim of this thesis is the comparison of different cooling methods and the influence of several hot working steels with advanced thermal conductivity on heat extraction. Experiments simulate the situation of core cooling during the high pressure die casting process. Different standard elements as inserts for the core and cooling media (i.e. water cooling, oil cooling, jet cooling and CO2 cooling) are tested and evaluated. Furthermore, the influence of hot working steels with advanced thermal conductivity on the cooling efficiency is tested.