A description of the important physical metallurgy aspects of Ni3Al and NiAl encompassing structure, crystallographic defects, slip systems and phase stability has been presented in this article. The microstructures generated in the two alloys by conventional as well as novel processing techniques have been discussed. The effect of alloying additions on the microstructure has been enumerated. Besides description of the aforementioned physical metallurgy aspects, an important purpose of this review is to focus on the reasons of brittleness in the two alloys and means of alleviating this problem primarily by alloying. The effect of alloying on the slip behaviour has also been described.