The response behavior of coated acoustic plate mode (APM) devices upon exposure to ionic solutions was evaluated. The response sensitivity (frequency shifts and attenuation) of APM devices coated with porous oxide films increased by factors of ca. 4-30 compared with an uncoated device upon exposure to ionic solutions. These responses arise predominantly due to acoustoelectric coupling and are consistent with enhanced pore conductivity. A previously derived model for the acoustoelectric response of uncoated APMs is inadequate for predicting the magnitude of coated APM responses and needs to be modified to account for the properties of porous films. Frequency responses are consistent with enhanced conductivity of the solution within the porous coatings. Film porosity, pore size distribution, and film thickness are identified as parameters influencing response sensitivity. 21 refs., 9 figs., 2 tabs.