The composition of NixPdy (x, y = 1, 5) and NiMoRe alloys irradiated by 3 and 4 keV Ar+ ions along the normal to the sample surface was investigated in situ by low energy ion scattering spectroscopy (LEIS). The analysis was performed using a 5 keV Ne+ ion beam. It was found that the composition of the topmost layer of bombarded NixPdy alloys nearly corresponds to the alloy stoichiometry. In the case of irradiation of the NiMoRe alloy, a surface enrichment with the heavier components (Mo and Re) was found. The thermally activated Gibbsian segregation in NiPd and NiPd5 alloys was also studied using LEIS.