The chemical composition of CuInSe2 (CIS) thin films was determined through an electrochemical method implemented in our laboratory. The CIS thin films were grown on soda lime glass substrates by the chemical reaction of their precursors occurred in a multistage process. The quantitative determination of the elements constituting the CIS films was carried out by Differential Pulse Stripping Voltammetry (DPSV). Comparing the results obtained by the electrochemical analysis with the phases identified in the CIS samples by XRD (X-ray diffraction) measurements, it was found that the DPSV method is reliable. The studies revealed that the samples grow in the α-phase (CuInSe2) and crystallize in the chalcopyrite structure, which is of technological interest in the photovoltaic industry. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)