Unoccupied electronic states of an ordered (1×1) Sb overlayer on cleaved GaAs(110) and InP(110) surfaces are studied by angle-resolved inverse photoemission. A well-ordered overlayer is obtained by thermal annealing after room-temperature deposition of Sb onto freshly cleaved surfaces. At we observe a clearly resolved Sb-derived surface resonance at 2.1 eV above the valence-band maximum for GaAs as well as for InP. An upward dispersion of the Sb state of 0.2 eV is found towards X. © 1988 The American Physical Society.