Viologens adsorbed on TiO2 surfaces in nanocryst.-nanoporous electrodes were studied with regards to the electrochromic effect. The transparent nature and the high internal surface area of these electrodes are very beneficial in this regard. Absorbance up to 1 and coloration efficiencies >100 cm2C-1 were obtained. The switching times for these electrodes for both coloration and bleaching were faster than 1s, using 0.5M LiClO4 in MeCN as electrolyte. Preliminary stability tests were performed. For one of these electrodes the authors went through 654 cycles of coloration and bleaching without a decline in the coloration efficiency.