We performed a comprehensive study on the electrochromism in TiO2 thin films made by reactive DC magnetron sputtering and elucidated the roles of sputter gas pressure p, O-2/Ar gas ratio gamma and substrate temperature tau(s). Good mid-luminous optical modulation taken to be similar to 50% in similar to 200-nm-thick films was obtained under charge exchange in a Li+ electrolyte for p > 15 mTorr and tau(s) < 100 degrees C, whereas gamma was less important. The deposition rate dropped for increasing p, and hence p approximate to 15 mTorr was optimal. These films were X-ray amorphous and contained some water. The coloration efficiency eta was 25 cm(2)/C, which exceeds data on eta in most prior studies on sputter deposited TiO2 and verifies that such films can display the same values of eta as those of TiO2 films made by several chemical techniques. (C) 2013 Elsevier B.V. All rights reserved.