Radiation-Induced Segregation (RIS) has been investigated in concentrated Ni-Cu alloys (Ni-10 at% Cu and Ni-60 at% Cu) in a temperature range between 470°C and 610°C. Depth profiling using Auger Electron Spectroscopy (AES) as well as in situ Rutherford Backscattering Spectrometry (RBS) revealed significant segregation of Ni to the surface during ion irradiation. The width of the segregated region was found to increase with increasing temperature, extending to ∼170 nm at 610°C. A post irradiation annealing experiment is presented to show that the segregation is radiation-induced. The results are discussed in the framework of current models of RIS with the aim of identifying the possible origin of the segregation.