Surface excitation parameters and inelastic mean free paths of electrons are of importance in the analyses of surface sensitive electron spectroscopies. When probe electrons are near the surface of a solid or the interface of an overlayer system, electron inelastic mean free paths become depth-dependent. These mean free paths and surface excitation parameters were calculated for electrons crossing the surface of GaAs. Calculations were performed for both incident and outgoing electrons by the use of a dielectric response theory. Applications were made to estimate the elastic backscattering intensity of electrons at different emission angles using the Monte Carlo simulations. Good agreement was found between calculated results and experimental data on the ratio of the elastic reflection coefficient for a GaAs sample relative to a Ni reference. Such a ratio was used to determine the effective electron inelastic mean free paths in GaAs by employing the surface excitation parameter obtained from Monte Carlo simulations. (C) 2004 Elsevier B.V. All rights reserved.