A new Ag+ ion conducting composite electrolyte system (1-x)[0.75 AgI:0.25 AgCl]:xSnO(2) using a quenched/annealed [0.75 AgI:0.25 AgCl] as host compound in place of conventional host AgI, has been investigated. The effects of various preparation methods and soaking time are reported. The composition 0.8[0.75 AgI:0.25 AgCl]:0.2SnO(2) exhibited optimum conductivity (sigma = 8.4 x 10(-4) S/cm) with conductivity enhancement of similar to 10(1) from the annealed host at room temperature. Transport property studies such as electrical conductivity (sigma) as a function of temperature using impedance spectroscopy technique, ionic transference number (t(ion)) using Wagner's d.c. polarization method and ionic mobility (mu) by transient ionic current technique were carried out on the optimum conducting composition. The mobile ion concentration (n) was calculated from 'sigma' and 'mu' data.