The electrochemical quartz crystal impedance system (EQCIS) has been used for the study of a partially immersed An electrode in 0.2 mol/L NaCIO_4. aqueous solution. The influences of the immersed area and height of the electrode on the EQCIS responses were evaluated, showing the highest response sensitivity to liquid loading at the center of the piezoelectric quartz crystal electrode. The increase in the immersed height of the An electrode at oxygen reduction potentials during potential cycling was measured by this technique. The influences of the immersed area and height of the electrode on the EQCIS responses were expressed as electrode on the EQCIS responses were evaluated, showing the highest response sensitivity to liquid loading at the center of the piezoelectric quartz crystal electrode. The increase in the immersed height of the An electrode at oxygen reduction potentials during potential cycling was measured by this technique.