Glasses based on the ternary oxide system Cu2O-TeO2-MO3 (M = Mo or W) doped with CuI were synthesized according to the formula zCuI . (1 - z){xCu(2)O . (1 - x)[yTeO(2) . (1 - y)MO3]} (M = Mo, z = 0.3, 0.4 and 0.5 and M = W, z = 0.3 and 0.4, respectively) in vacuum or argon atmosphere using the twin-roller quenching technique. The glasses exhibit phase separation and in most compositions a-CuI crystallites are stabilized at room temperature as confirmed by XRD and HRTEM. The highest ionic conductivity at 298 K is similar to 3 X 10(-4) S cm(-1). The Arrhenius plots show a break in the temperature range 294+/-5 K with sigma increasing from 10(-5) S cm(-1) to 10(-4) S cm(-1). The conductivity below 294 K and above 295 K is due to the ionic conduction by Cu+ in the oxide glass matrix and the halide phase, respectively. DSC studies do not show any phase transition in the region 294+/-5 K. FTIR study indicates that the IR bands of glasses are not affected by doping of CuI. XPS studies show that the fractional area of Cu 2p peaks [Cu+/(Cu+ + Cu2+)] are in the range 0.35-0.61 and 0.44-0.72 for systems with M = Mo and W, respectively. The average fraction of non-bridging oxygen (NBO) is higher than that in the corresponding oxide glasses without the CuI dopant.