The band structure of Ga 1 - x Al x P under a uniaxial stress is calculated in the virtual crystal approximation (VCA) using the empirical pseudopotential method (EPM). We discuss the optical transitions in this system under a static uniaxial compression and a tension along a cubic direction [100], on the light of the change in energy caused by these stresses for states of high symmetry near the top of the valence band and the bottom of the conduction band.