The understanding of the very early stage of copper crystal formation kinetics and mechanism is very important for both fundamental and applied aspects. Particularly the quality of the industrial electrolytic copper deposit can be improved and better controlled. In this paper, copper nucleation mechanism is investigated in real refinery electrolytes. The main aim is to study the influence of potential, temperature and copper concentration on potentiostatic reduction of copper ions. The model of electrocrystallization is considered on the basis of the equations describing the nucleation controlled by diffusion towards a disc-shaped ultramicroelectrode. in the present paper the rates of copper nuclei formation are estimated tinder different applied potential, temperature, copper and levelling agent concentrations. (C) 2008 Elsevier Ltd. All rights reserved.