The site and nature of the bonding of H at a Ti (0001) surface are established via the analysis of new angle-resolved photoemission measurements by self-consistent electronic-structure calculations. Experimentally observed H-induced surface states are identified with calculated bonding and antibonding combinations of H 1s and Ti 3d, 4s orbitals. The positions of these levels are strongly dependent on local bonding geometry. The H site which minimizes the total energy gives a very good account of the observed spectrum. Ignoring the total energy leads to a more ambiguous structure determination. © 1980 The American Physical Society.