Cast nickel-base superalloys possess the required mechanical properties (creep resistance and stress rupture life) at elevated temperatures that make them suitable for turbine blades in aero-engines. The origin of these properties lies in the presence of a simple two phase gamma-gamma' microstructure (with cuboidal gamma' particles dispersed in a gamma matrix), in spite of the presence of several alloying elements. The cuboidal nature of the gamma' particles arises from an optimal misfit between the two phases, which is a function of the composition of gamma and gamma' phases. In addition, several microstructural issues arising out of the partitioning of the alloying elements influences directly the deformation mechanisms in the gamma and gamma', and therefore the mechanical properties of the alloy. In this article, we discuss how some of these microstructural issues have been investigated in DMS4, a cast single crystal superalloy, experimentally using TEM and 3DAP techniques.