Automotive turbocharger housings are complex castings of predominantly thin section requiring a demanding combination of properties. Ni-resist Type D5S, a highly castable austenitic ductile iron containing 36%Ni, 5.3%Si, 2%Cr, provides the required combination of properties and is finding increased application in turbo-charger housing. A series of investigations has been conducted into the influence of melting/casting and compositional variables on microstructure, mechanical and physical properties, and machinability of this iron. A preferred melting/casting practice is recommended, and the effects of various addition elements are defined. Mechanical, physical, machinability and oxidation properties are presented.