Tracer grain-boundary diffusion of 6 3 Ni in slightly hypostoichiometric (x A l <25 at.%) Ni 3 Al alloys containing several percents of Cr, Fe and Zr was studied using both serial sectioning and residual activity methods. Measurements of grain-boundary diffusivity P were carried out in the temperature interval 873-1273 K. It was found that the additions of Cr, Fe and Zr decrease the P and increase the activation enthalpy of 6 3 Ni grain-boundary diffusion.