In order to test the low-energy electron diffraction (LEED) "underlayer" geometry of the Ti(0001)-N(1×1) system we have carried out self-consistent electronic-structure calculations and a variety of ultraviolet-photoemission-spectroscopy measurements. The assumption of the Shih et al. underlayer geometry yields the correct N-2p level ordering at and the correct directions of dispersion along -M. The positions of these levels are calculated to within 0.7 eV. The Fermi-level surface state predicted earlier for clean Ti(0001) is observed experimentally and, as predicted by the present calculations, is not quenched as the N adlayer forms. This result indicates that the outer Ti layer screens the potential due to N quite effectively. A layer of H on the Ti(0001) surface is found to quench the Fermi-level surface state, as predicted in the overlayer calculations of Feibelman and Hamann. © 1980 The American Physical Society.