The electronic properties of H chemisorbed on the Pd(111) surface are studied using a self-consistent pseudopotential mixed-basis method. The H atoms are predicted to prefer a threefold hollow over the top site. Strong bonding between hydrogen and the substrate results in (a) dramatic changes in the surface electronic structure and (b) the formation of bonding and antibonding adsorbate states. The combined effects of both accurately reproduce and explain the salient features of recent photoemission measurements. © 1979 The American Physical Society.