Tracer volume diffusion of 63 Ni in Ni-50.07 at.% Ti binary and Ni-48.83 at.% Ti-9.29 at.% Cu ternary alloys have been measured between 783 and 1288 K. The temperature dependence of the diffusion coefficients can be well described by a straight Arrhenius function This illustrates that a diffusional anomaly , if there is any in this system, is negligible. On the other hand, the small activation energy shows that the mechanism of diffusion is probably mediated by structural vacancies.