Heteroepitaxial GaP layers were grown on Si substrates, misoriented by 5° from the (111) face toward the [100] axis, by molecular beam epitaxy (MBE). The RHEED pattern of GaP is of elongated streaks, indicating that the quality of the grown layers is good. From observation by the X-ray divergent beam method, the [111] axis of the grown layers is parallel to that of the substrate. Autodoping of Si into the epitaxial layers from the substrate is very small compared with the layers grown by CVD. Photoluminescence was measured for GaP on Si which was irradiated with an ionized nitrogen beam during MBE.