Electrogencration of soluble Prussian Blue (PB) during the oxidation-reduction of the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) system has been detected using bidimensional spectroelectrochemistry (BSEC). This new technique allows us to obtain simultaneously two different spectroscopic signals together with an electrochemical signal, each one containing different information. Starting from pure Fe(CN)(6)(4-) solutions, some experimental conditions under which soluble PB appears, have been analysed. Fe(CN)(6)(4-)/supporting electrolyte concentration ratio and potential scan rate have been found as the most influential factors. All experiments show clearly the generation of soluble PB but in no case the insoluble form has been detected. From the results, PB generation can be explained as a surface chemical process coupled with the electron transfer reaction. (C) 2003 Elsevier Ltd. All rights reserved.