Fe/ZnSe(0 0 1) system is attracting interest because it is one of the rare successful example of ferromagnetic metal-semiconductor epitaxy, where both chemistry and magnetic properties of the interfaces remain stables up to 600 K. This can be very important in view of the production of spintronics devices. Epitaxial Fe films with thickness in the range between 0.7 and 5 nm were deposited on ZnSe(0 0 1) in ultra-high vacuum. Thermal spin-waves were detected in situ using Brillouin light scattering, i.e. inelastic scattering of light by thermal spin-waves. The evolution of magnetic anisotropy with Fe film thickness has been studied. Even if at large film thickness the expected biaxial anisotropy of magnetocrystalline origin is present, for low coverages an uniaxial magnetic anisotropy (UMA), of interface origin, dominates, in agreement to what previously observed in the Fe/GaAs system. Different from this latter system, however, we have verified that the introduction of a Cu capping layer, as well as annealing to high temperature, do not appreciably alter UMA in Fe/ZnSe films with thickness larger than I run, suggesting that the physical mechanism responsible for the rise of the UNIA is more stable in the Fe/ZnSe than in Fe/GaAs. (C) 2007 Elsevier B.V. All rights reserved.