Predictions of band offsets assign a type‐II offset for the GaAs–InP interface without inclusion of strain effects, with the conduction‐ and valence‐band‐edge offsets approximately given by 0.4 and 0.3 eV, respectively. It has been demonstrated recently that pseudomorphic GaAs grown on [100]‐oriented InP also has a type‐II interface, but with the conduction‐band offset reduced by the hydrostatic deformation potential of GaAs. Poisson’s ratio in GaAs for [111]‐directed uniaxial stress is smaller by 40% than the value for [100]‐directed stress. The lattice constant perpendicular to the growth interface is therefore not reduced as much for [111]growth compared with the [100]‐growth case, leading to a consequently larger shift of the conduction‐band‐edge energy. Based on the recently measured value of −9 eV for the conduction‐band‐edge hydrostatic deformation potential in GaAs, the band offset for pseudomorphic GaAs grown on (111) InP has been calculated to be type I. This material system should therefore show type II to type I conversion dependent on the growth direction of the pseudomorphic layer. The issues involved in the growth and measurement of GaAs grown on (111) InP are discussed briefly.