Diffusion of chromium in pure nickel has been studied by radioactive tracer and residual activity technique. The diffusion coefficient (in units of cm2/sec) in the range 600°−900°C is given byDCr/Ni=0.03 exp(−40 800/RT) and in the range 350°−600°C is given byDCr/Ni=5.45×10−9exp(−13 700/RT).The bimodal diffusion behavior has been explained on the basis of solid solubility of chromium in nickel, which falls very rapidly from 1000°C downwards. The entropy of activation for high‐temperature diffusion falls very well on the entropy vs activation energy curve for lattice diffusion in nickel.