A new layered perovskite compound, Ag 2 La 2 Ti 3 O 1 0 , was synthesized by an ion-exchange reaction of M 2 La 2 Ti 3 O 1 0 (M = Na,K) with a AgNO 3 molten salt. The crystal structure and the ionic conductivity of the ion-exchanged compound were investigated. The ionic conductivities attributed to the interlayer silver ions were observed at high temperatures. The ionic conductivity of Ag 2 La 2 Ti 3 O 1 0 was much higher than that of Na 2 La 2 Ti 3 O 1 0 , while the interlayer sodium ions in Na 2 La 2 Ti 3 O 1 0 and silver ions in Ag 2 La 2 Ti 3 O 1 0 have almost the same rock-salt type coordination. The higher conductivity of Ag 2 La 2 Ti 3 O 1 0 is probably due to the higher polarizability of silver ions.