We report an electrochemical approach to form crystalline CuInSe2 (CIS) films onto indium-tin-oxide substrates via thermal treatment to Se-coated Cu-In alloy. The simultaneous deposition of Cu-In alloy with optimum thickness was obtained by an electrochemical method from a mixture of aqueous solutions of CuSO4 and In-2(SO4)(3) at constant potential. Further, the electrochemical method was used for deposition of elemental Se onto the priorly deposited Cu-In alloy film. To produce CIS films, Se-coated Cu-In alloy films were annealed in argon atmosphere at different temperatures ca. 350-450 degrees C for 30 min. The Cu-In alloy, Se-coated Cu-In alloy, and thermally treated films were characterized using X-ray diffraction to identify the phases and scanning electron microscopy to observe the surface morphology. (C) 2008 The Electrochemical Society.