We present a scanning tunneling microscopy (STM) study of the initial stages of ZnSe deposition on the GaAs(001)-(2×4)surface. The deposition of elemental Se and of ZnSe on the bare GaAs surface induces considerable atomic disorder attributed to the Se–As exchange reaction. The deposition of elemental Zn weakens the2×periodicity of the surface but induces no apparent changes in the STM images of the As dimers. Comparison of STM images of submonolayers of ZnSe on GaAs with and without a Zn pretreatment suggests that Zn reduces the interaction of Se with the GaAs surface. ©1997 American Institute of Physics.