"Nanosecond" electrochemistry is used to investigate the impacts of various solid particles (alumina and graphite suspended in aqueous perchloric acid and copper suspended in aqueous sodium perchlorate) at a polycrystalline gold electrode under insonation. Current spikes of microsecond duration, attributed to individual impacts, are observed under potentiostatic conditions, with a polarity that inverts at the potential of zero charge of the electrode/electrolyte system. It is found that there is no significant change in the magnitude of these transients as the sizes of alumina particles range from 0.3 to 25 mum. However, appreciable changes are observed in the transients when using electroactive particles, specifically graphite powder surface modified with adsorbed N,N'-diphenyl-1,4-phenylenediamine, and evidence is presented for the occurrence of electron transfer during the impact event which occurs on the sub-microsecond time scale.