DTA and powder x-ray diffraction measurements allowed to draw the phase diagrams of the systems AgI-Ag2XO4 (X = Cr, Mo, W). A more detailed investigation was devoted to the composition range around XAgI = 0.8, where in preliminary tests it was observed that the room temperature ionic conductivity strongly depends on the thermal treatment of the sample. By quenching mixtures at XAgI = 0.8, glass-like phases with high conductivity were obtained; in the systems AgI-Ag2CrO4 and AgI-Ag2MO4 the subsequent crystallization gave rise to non con-ducting phases, whereas the occurrence of the highly conducting compound 4AgI·Ag2WO4 was recognized in the third system investigated.