An investigation of the ionic conductivity in sodium chloride (NaCl) crystals doped with different concentrations of yttrium (Y) is undertaken in the temperature range 1800C to 5250C to understand the nature of impurity vacancy (I-V) complexes, their formation and howthese I-V complexes affect the conduction process. The conductivity temperature plots of NaCl: Y showed two distinct regions. These regions are explained on the basis of Dreyfus and Nowick notation. It is found that ionic conductivity in Y doped NaCl crystals decreases with increasing Y concentration. Quenching and annealing studies indicate that the ionic conductivity increases due to the former and decreases due to the later. Possible mechanisms for the above results are explained in terms of formation of various defects such as IV complexes, vacancies, etc.