Ionic conductivities of hydrated zeolite Li-, Na- and K-A at room temperature and at pressures up to 4.8 GPa have been measured. Anomalous increases in conductivity with pressure up to 1.7-1.9 GPa were observed for all zeolites. In this pressure range, activation volumes of conduction are -1.4, -3.9 and -6.8 cm(3)/mol for Li-, Na-and K-A zeolites, respectively. The conductivity goes through a maximum, where pressure-induced amorphization occurs. Following the maximum, there is a rapid decrease in conductivity due to the collapse of long-range ordering. On decompression, conductivity increases to values that are higher than the conductivity values at equal pressures on compression.