The existence of both empty and filled surface states derived from the rehybridization of dangling Sb bonds is demonstrated for the first time in GaSb. The empty states are nearly degenerate with those derived from dangling cation bonds and are located near the bottom of the conduction band. The filled states lie ∼0.8 eV below the valence-band edge. Similar sets of states were observed for Sb adsorbed on GaAs and InAs. © 1977 The American Physical Society.