In this work we describe the assembling of a solid-state electrochromic device using, as active materials, an organic conductive polymer and a transition metal oxide. The optically active materials were dodecylsulfate doped polypyrrole and tungsten oxide. The substrates used were glass slides coated with tin-doped indium oxide and the solid elastomeric electrolyte was the copolymer of ethylene oxide and epichlorohydrin containing lithium perchlorate. Initially, we studied separately the materials used to assemble the device and, in sequence, we assembled and characterized the complete devices. The thickness of the polypyrrole and the electrolyte films were varied to obtain the highest chromatic contrast, stability over a high number of redox cycles, and short response times. The characterizations were made by spectroelectrochemistry using the techniques of cyclic voltammetry and chronoamperometry : To illustrate the results obtained, we describe two devices with different polypyrrole and electrolyte film thicknesses. The chromatic contrast in the visible and near-infrared wavelength range is 30% and the electric and optical properties of the devices remain unchanged after 1.5 X 10(4) double potential chronoamperometric steps.