The effects of light irradiation of a He-Cd laser (441.6 nm) on MBE growth of ZnSxSe1-x (x=0-0.13) were studied. The growth rates of the epilayers were reduced and the photo-desorption rate constanSts of Zn, Se and S were obtained. In the photoluminescence spectra at 11 K, the intensities of the free exciton emission increased, and thus the crystallinity of the epilayers was found to be improved. The behavior of surface adatoms on the growing surface under laser irradiation is discussed. © 1989.