We present the first perturbed angular correlation observations of defect complexes in the technologically important material (Hg,Cd)Te. In particular, we report the observation and identification of In-mercury vacancy complexes in Hg 0.79Cd 0.21Te. These complexes were observed following a rapid quench of the material after annealing at 350-400 ° C in vacuum. Since the complexes vanished following similar quenching in a Hg atmosphere, we conclude that they involve Hg vacancies. The migration energy of vacancies was calculated to be 0.6 ± 0.2 eV from measurements of the evolution of the In-V Hg complexes during annealing between 75 and 100° C.