The evolution of valence hand photoemission spectra in the formation of noble metal-GaAs (110) interfaces has been studied with 21.2 eV and 40.8 eV photons. For less than 0.5 mono-layer of deposited metals, the so-called atomic-like Ag 5s and Au 6s states have been observed. A maximum in the emission of the valence band of noble metals has been observed in the range from about 10 ? to a few tens ? of deposited metals. The experiment results are discussed with the point of view of metal clustering associated with interfacial reaction.