The electronic structure of two-dimensional, ordered Pb overlayers in submonolayer coverages on MBE grown GaAs(001) surfaces has been studied by angle-resolved photoemission using synchrotron radiation. A Pb(6s) derived interface state of Δ1 symmetry has been identified in the heteropolar gap of GaAs at an energy of −8.3 eV below the valence-band maximum. Two surface resonances of dangling bond character and of inplane character ( px−py) are located near the top of the valence bands, at −0.4 eV and −2.0 eV, respectively. High resolution studies of Ga(3d), As(3d), and Pb(5d) core levels show that there is no significant chemical interaction between the overlayer and the substrate.