A transient natural convection develops along vertical plane Cu electrodes during the galvanostatic electrolysis. The time variations of both the concentration profile of CuSO4 and the velocity profile of a 0.6 M CuSO4 aqueous electrolyte were measured. The mass transfer rate of Cu 2, ion as well as the natural convective fluid motion was analyzed. The effect of electrode spacing on the transient natural convection was focused. The overshooting phenomenon caused by the transient diffusive and convective mass transfer rate was observed. Numerical simulation may provide as better understanding of the phenomena. (C) 2007 Published by Elsevier Ltd.