Ni Al, an interrnetallic compound with the B2 ordered structure. exhibits potential as a viable high temperature structural material. However. before this material (and other interrnerallics) can be of practical use a number of technical problems must be overcome. including lack of ductility al the room temperature. In an attempt lO address the brittleness of NiAI. and based on a premise that grain refinement may lead lo significant ductility improvements mechanical alloying and nanocrysialline synthesis were used to produce fine-grained NiAI. The mechanically alloyed NiAI with an average grain size of about 0.5 μm, unlike its coarse grained. cast counterpart, exhibits a notable room temperature compressive ductility due to two contributing microstructural factors: i) the development of the< 110> texture during hol extrusion leading to the activation of additional slip systems. and ii) the predominance of low angle grain boundaries. In the nanocrystalline form, NiAI with an average grain size in the range from 2 lo I O nm, exhibits measurable room temperature ductility in biaxial disc bend tests. unlike its coarse-grained counterpart. This observation can be explained assuming that diffusional, rather than dislocation, mechanisms control plastic deformation of the nanocrysralline NiAI. The emphasis of the present paper is on rationalizing the improved room temperature ductility in mechanically alloyed and nanocrystalline NiAI. The most significant conclusion of the present discussion - contrary lo widespread beliefs - is that the grain size plays only an indirect role in controlling ductility.