Various reconstructions (c(2×6), (1×3) and (2×3)) of the GaSb (100) surface have been studied by LEED, XPS and UPS. All the three reconstructed surfaces are terminated by Sb atoms with some rows missing. Annealing in an Sb environment of both MBE-prepared, Sbdimerized c(2×6) reconstruction and IBA-prepared, Gaislands-existing (2×3) reconstruction leads to the same (1×3) reconstruction.