Diffusion studies were performed in the Au–Ni system over the temperature range 750–900°C. Interdiffusion coefficients were obtained by evaluating the concentration profiles of the annealed Au/Ni couples with the Sauer–Freise analysis. Intrinsic diffusivities DAu and DNi in various Au–Ni alloys, experimentally determined at 900°C by means of multi-foil couples, were compared with those predicted from the model of Darken–Manning with the aid of the thermodynamic and tracer diffusion data. The experimental values of DNi were close to those predicted by the model, while the intrinsic diffusivities of gold in the Au-rich alloys appeared to be considerably higher than the computed values. The experimental results are consistent with the relatively high Kirkendall-marker velocity within the zone of interdiffusion observed in the Au/Ni couples.