Electrochemical measurements of localized mass transfer effects within a cavitating liquid (sound field, 20-100 kHz) are reported. The contribution of acoustic streaming to mass transfer recorded at a microelectrode (Pt, 10 mu m diameter) is shown to be negligible in comparison to transient events. Active zones, within which high event density was observed, are shown to exist within the liquid. Transient events were recorded, within these active zones, at a frequency as high as ca. 4500/s, which was deemed the limit of resolution of the microelectrode and sort routine employed rather than a cavitation effect. These active zones are shown to be dynamic in nature. Average mass transfer coefficients within these active transient event zones of the order of 0.3 cm s(-1) are reported as well as the influence of acoustic pressure on mass transfer within these active zones. Photographic evidence indicates the volume and dynamic nature of the active cavitation zones within the cell.