The objectives of the project is to contribute to reduced emissions by weight reduction, which in this study is made by replacing the inner door steel structure with cast magnesium. Weight target is 55 % relative steel, implying vehicle lightening by more than 25 kg, hence saving 200 litre fuel during the life of the vehicle.A magnesium door concept is expensive in high volumes, and the risks include incomplete die filling, multimetal incompatibility and low strength. Cost efficiency implies to design for integration and commonality. Ductile alloys, correct ingate shape and optimized wall thickness is necessary to meet the impact and quality requirements of the door structure. Joining Al to Mg is mainly limited to adhesives and promising Mg surface treatment alternatives to chromateing have been evaluated.