Mo-Ti oxide films with compositions ranging from Mo oxide to Ti oxide were prepared by reactive DC magnetron sputtering. Electrochromic properties were studied in situ during Li ion intercalation. Colored films have a neutral gray appearance. Their stability improved when the Ti content was increased. Photochromic properties of Mo-Ti oxide films were investigated in order to clearly display polaron absorption bands. (C) 2000 Elsevier Science B.V. All rights reserved.