Ionic conductivity data for mixed Ag/Na-nitrite sodalites, AgNa(AlSiO)(NO), have been determined over the temperature range 250 to 550°C in ambient atmosphere using an ac impedance method. The activation energy for conduction is reported for five samples with silver contents ranging from x=0 to 7.5 and was found to be a monotonic function of silver content, with a minimum at the highest silver content. Conductivity isotherms for the mixed Ag/Na nitrite sodalites were constructed, showing a direct relationship of total ionic conductivity as a function of silver content, with fastest ionic motion at the highest silver content. A transition of conduction mechanism from Na ion predominance to Ag ion predominance with increasing x was confirmed from variations in the interfacial impedance characteristics. Ionic conductivity of nitrite sodalites is strongly dependent upon the ionic radius of the mobile cations incorporated.