Surface segregation is studied for CuxNi1-x alloys using the tight-binding Hartree-Hamiltonian and a mixed Bethe-lattice model to determine the electronic energy. Results for the surface segregation at (100) and (111) surfaces of the alloy are presented and compared with existing experimental results. Also, results are given for the temperature dependence of the segregation. Furthermore, the effect of the surface segregation on the local electronic density of states and on the surface core-level shifts is calculated on the basis of our electronic theory. {\textcopyright} 1982 The American Physical Society.