Cation and anion vacancy formation energies are calculated for HgTe, ZnTe, CdTe, and their dilute alloys. Harrison’s tight-binding theory is extended to a cluster embedded in an extended crystal. Only neutral vacancies have been considered and two final states for the removed atom have been addressed: a free atom in vacuum and an atom on an ideal (111) surface. Corrections caused by rehybridization of the dangling bonds and Coulomb energies resulting from charge redistribution have been included.