Calculations of expected X-ray photoelectron spectroscopy intensity ratios for both homogeneous and segregated bimetallic particles demonstrate that a minimum particle size exists, below which reliable differentiation between homogeneous alloy particles and particles in which one component has segregated to the surface cannot be made. This minimum particle size varies between 3 and 8 nm depending on the specific metal combination in question. In cases of partial segregation of one component, the minimum particle size is even larger. The implications of these results for the study of surface segregation in supported bimetallic catalyst particles are discussed.