The silver ionic conductivity in heterogeneous systems of AgBr:Al2O3 and AgI:Al2O3 is highly enhanced by utilizing mesoporous Al2O3 as the insulating phase. The highest Ag+ conductivity of 3.1 X 10(-3) Omega(-1) cm(-1) (at 25 degrees C) has been obtained for the AgI:Al2O3 composite with an Al2O3 volume fraction of 0.3. For AgBr:Al2O3, the enhancement of the conductivity is satisfactorily explained in the framework of the ideal space-charge model, while in the case of AgI:Al2O3 stacking disorder is also considered to contribute to the ionic conductivity.