Studies of some basic ionic transport properties of a new fast Ag+ ion conducting two-phase composite electrolyte system: (1 -x)[0.75AgI:0.25AgCl]:xZrO(2), where 0 less than or equal to x less than or equal to 0.5 tin molar weight fraction), are reported. A 'quenched/annealed [0.75AgI:0.25AgCl] mixed system/solid solution' has been used as a first phase host matrix salt as an alternative to the traditional host AgI, while particles (less than or equal to 5 mum) of the insulating and inert ZrO2 were dispersed as second phase dispersoid. In order to find the 'optimum conducting composition' (OCC), different compositions of the two phases were mixed homogeneously adopting various routes of preparation. The phase identification studies revealed the coexistence of separate phases. The temperature-dependent transport property studies were carried out on OCC employing various techniques. The mechanism of ion transport has been explained on the basis of models proposed for two two-phase composite electrolyte systems.