So far, the influence of sonication on the electrolytic current was studied only at solid or rather miniaturized mercury electrodes. The presented paper reports on sonoelectrochemical experiments at a liquid mercury pool electrode. Two sonoelectrochemical cells have been developed and tested. It was shown that during sonication, the electrolytic current increases in a number of individual peaks representing short local enhancements of current density due to vigorous local mass transfer and instantaneous increase of fresh electrode surface. Both these effects are caused by microjets of solution formed during violent unsymmetric collapses of cavitation bubbles in the close vicinity of the electrode surface. The newly formed electrode surface and the decrease in the diffusion layer thickness were estimated and discussed. An example is presented where the sonication is used for destruction of a film of products formed during electrolysis of cysteine, that otherwise rapidly inhibits continuation of the electrode process.