Scandium is added to aluminium alloys in small quantities to improve the mechanical properties by grain refinement. Additionally it enhances the ageing response of the alloys. These alloys are normally used in the wrought condition. The present investigation reports the microstructure and properties of Al-Mg-Sc-Zr alloys produced by investment casting. The casting conditions are optimized to get a material which could be aged without the customary solutionising treatment prior to the ageing. Finer matrix grains associated with nano sized precipitates result in very attractive combination of strength and ductility. Good dimensional accuracy is obtained because of the investment casting and elimination of solutionalising treatment. The material and the process are highly suitable for aerospace applications.