The structure of the GaSb(110)(1 x 2)-Bi reconstruction has been solved using surface x-ray diffraction, scanning tunneling microscopy, and photoelectron spectroscopy. The ideal GaSb(110) surface is terminated with zigzag chains of anions and cations running in the [1 (1) over bar 0] direction. In the Bi-induced (1 X 2) reconstruction we find that every second zigzag chain in the uppermost substrate layer is missing. The reconstructed surface is terminated with a full monolayer of Bi atoms which also form zigzag chains. The Bi atoms in the chains bond alternately to the first and second layer substrate atoms and the Bi chains are inclined at 34 degrees to the (110) plane. [S0163-1829(97)03335-3].