This paper presents data on experimentally and theoretically deduced total energies and energy level positions in the band-gap for eight elementary defects in CdTe. Based on these data, the total energy dependence on the Fermi-level position in the band-gap is graphically analysed. Two types of defect reactions, which are responsible for cadmium vacancy (V Cd) creation and transformation, are discussed. It is shown that the most probable candidate for the native deep-level donor is a tellurium antisite.