Room temperature electroreflectance measurements have been made on samples of AlxGa1−xAs alloys, grown by liquid epitaxy. The variation of the different band transition energies, E0, E1, E2, etc. has been determined as a function of composition x. For each transition energy, the data have been fitted to the relation E = a + bx + cx2 and hence the bowing parameter c determined. These experimental values of c are compared with the predicted values of Van Vechten.