Layers of TiO2 nanotubes have been fabricated by electrochemical anodization of Ti. After annealing the tubes to an anatase structure Cr doping was carried out by ion implantation at an energy of 60 keV and at two nominal fluences, 5 x 10(15) cm(-2) and 5 x 10(16) cm(-2). XRD measurements reveal that the anatase structure shows a certain degree of 'amorphization' after ion implantation. However, this effect can be reversed by subsequent thermal annealing. Photoelectrochemical measurements show a visible photoresponse for the Cr+ implanted tubes. Reannealing the tubes, leads to an increase in the photoresponse magnitude in the visible range of the solar spectrum. (c) 2006 Elsevier B.V. All rights reserved.