Abstract The segregation kinetics of sulfur on the Ni (100) surface has been investigated by means of AES during heat treatment of the sample between 650℃ and 800℃. The concentration of segregated sulfur is proportional to the square root of time in agreement with McLean's model. The temperature dependence of the diffusion coefficient D is D(cm2/s) = 5×10-3 exp(-44600/RT). The LEED experiment shows that the saturated sulfur layer has a c(2×2)-S structure at room temperature. Depth profile analysis shows an exponential decrease of (S/Ni) Auger peak height ratio with time during argon ion bombardment.