Commercially pure titanium substrates have been treated using Q-switched Nd:YAG laser radiation (tau = 50ns, lambda = 1.06 mum). The repetition of laser shots at the same location induces thermal cycling which leads to progressive oxidation and to the formation of multilayered coatings [1.2]. Previous studies have given us an overview of the various titanium oxides which could be formed as a function of the laser treatment parameters. This work focuses on the very early stage of the laser-induced oxidation, when the oxygen content does not exceed 50 at,% MO). The treated layers have been characterized by optical and SEM observation, EDS and X-ray diffraction analyses. The presence of the different new structures has been examined in relation with the Ti-O phase diagram. (C) 2002 Published by Elsevier Science B,V.