Alloys based on the B2 compound NiAl have significant potential for applications in hot sections of aircraft engines due to their low density, high melting point, and high thermal conductivity. A major disadvantage of this class of materials is low ductility at ambient temperatures. Recently, it was discovered that small levels of certain elements (eg. Fe, Ga, Mo) result in dramatic improvements in room temperature ductility. In this paper, results are presented from a mechanistic investigation of the “microalloying” effect. Tensile and compression testing as a function of temperature and orientation has been performed on both the binary compound and microalloyed material. Data on ductile to brittle transition temperatures, critical resolved shear stress values as a function of temperature on the different slip systems, and dislocation structures from TEM analysis of the tested specimens are presented. These data are discussed in terms of possible mechanisms for the microalloying effect in NiAl alloys.