A deep state possessing similar properties to those reported forDXcenters in the AlGaAs system has been observed at atmospheric pressure in GaSb moderately doped with sulfur. The first detailed deep level transient spectroscopy study of this material has revealed a large energy barrier to electron capture and a correspondingly small capture cross section for this deep level. The deep level activity of selenium‐ and tellurium‐doped GaSb has also been investigated.