A novel thin film growth technique, photo-assisted homoepitaxy of ZnS usingmolecular beam epitaxy (MBE), has been carried out with elemental zinc (Zn) and elemental sulphur (S) as source materials. The crystallinity of ZnS was greatly improved by irradiation with 350 nm monochromated ultraviolet light from a xenon lamp. The growth rate was about 0.6 μm/h at 260°C. The crystal quality was characterized by RHEED patterns, surface photographs and photoluminescence spectra. Finally, the irradiation intensity dependence and the growth mechanism were discussed. © 1989.