Elastic constants of zinc-blende GaAs chi Sb1-chi, are calculated from the framework of the pseudopotential method within the virtual crystal approximation combined with the bond-orbital model of Harrison. These constants are used to calculate the sound wave velocities propagating in different directions in the material of interest. A particular attention has been devoted to the effect of compositional disorder. For this purpose, a correction to the alloy potential has been introduced. Numerically calculated values show reasonable agreement with known data. Comparisons between our results and those of interpolation schemes reported in previous studies suggest that the applicability of the linear interpolation approaches for the properties being studied for the alloy under consideration is possible. (c) 2005 Elsevier B.V. All rights reserved.