This paper describes the high-pressure die castability assessment of two high temperature magnesium alloys, AE42 and the AC series alloy.AE42 is a commercially available alloy. Results showed that AE42 was a castable material for use in high-pressure die casting applications, including large transmission components. AE42 was determined to have similar operating/manufacturing costs if produced in equivalent volumes to AZ91D.The AC series alloy is an experimental alloy comprised of AM50 combined with small percentages of calcium (Ca). It was found that the castability of the AC series alloy decreased with increasing calcium content. Over 0.3% calcium content yielded poor castability performance.Selected mechanical and corrosion properties of AZ91D, AE42, AM50 and the AC series alloys were also explored.