Evaluation of electrical transport and structural characteristics of the pseudo ternary system 40(Cu1-xAgxI)-45(Ag2O)-15(B2O3), where 0.05 less than or equal to x less than or equal to 0.25 has been reported. Electrical conductivity measurements were made using complex impedance method. The extent of contribution of ionic conductivity to the total electrical conductivity in various compositions of the above system was determined by evaluating their ionic transport numbers (t(i)) using Wagner's method and the corresponding silver ionic transport numbers (t(Ag+)) by the E.M.F. technique. These measurements have indicated the formation of superionic materials having electrical conductivities of the order of 10(-4) to 10(-3) S cm(-1) at room temperature. X-ray diffraction (XRD) analysis, differential scanning calorimetry (DSC) and fourier transform infrared (FT-IR) spectroscopic investigations carried out on these materials have indicated the composite nature of these superionic solids consisting of glassy and crystalline phases. Thermoelectric power (TEP) measurements have also confirmed the positive charge on the conducting species and activation energy for conduction in these materials.