Novel compounds, AgLaTiO4 and AgEuTiO4, have been synthesized by an ion-exchange reaction from parent compounds, NaLaTiO4 and NaEuTiO4. The crystal structure of the silver ion-exchanged compounds was determined by the Rietveld analysis for powder XRD patterns. The silver ion-exchange compounds retain the structural characteristics of the parent phases. The interlayer silver ions in the silver ion-exchanged compounds have a rock-salt type coordination. These compounds, which are probably metastable, could only be obtained by the ion-exchange reaction. The ionic conductivities attributed to the interlayer silver ions were observed at high temperatures. The ionic conductivity of AgLaTiO4 was much higher than that of NaLaTiO4. Such a high ionic conductivity is probably due to the higher polarizability of silver ion.