Photoemission measurements are used to study the Schottky barrier formation and the intermixing (with GaAs) of the three metals, Cu, Ag, and Au, deposited at room temperature on GaAs(110) cleaved surfaces. It is tentatively concluded that Fermi level pinning cannot be followed satisfactorily for metal coverages above a monolayer. The work of Palau on Schottky barrier height (I–VandC–V) for Au and Ag deposited on cleaved GaAs(110) in UHV indicate pinning positions surprisingly close to those found for other overlayers in the ‘‘unified defect’’ model. It was found that ‘‘intermixing’’ between noble metals and GaAs decreases in the order of Cu, Au, and Ag. Although island formation probably occurs, it is tentatively concluded that the principle reason for difficulty in using our photoemission measurements to determineEfsfor the noble metals is the inclusion of Ga (as well as As) in or on the noble metal overlayer.