The dependence of the barrier height φBn of Au-Ga1−xAlxSb Schottky barriers on x, the mole fraction of Al in the solid, has been measured. The data show that as x increases the values of φBn also increase. However, the measured barrier heights do not agree with those predicted by the ‘common anion’ rule. This result, coupled with other available data, indicates that the Au-Ga1−xAlxSb hole Schottky barrier height (φBn) is not independent of the Ga/Al cation ratio.