The aim of the present paper is to provide an overview of the recently introduced root canal single file preparation system, One Shape (Micro Méga, Besançon, France). In contrast to some other single file systems, the One Shape file is used in continuous rotation, as known from many former multiple file rotary NiTi systems for root canal preparation. The unique design of the One Shape instrument incorporates a variety of different cross sections along the active length of the file, which offers an optimal and improved cutting action in three zones of the root canal. Each instrument has been electropolished to enhance cutting efficiency. One Shape's flexibility and unique downward movement ensures a highly effective apical progression. Minimal fatigue along the length of the entire file virtually eliminates the risk of accidental instrument separation. The One Shape instrument is actually available with a safety tip in size 25 at the tip with a continuous 0.06 taper. It is delivered in a sterile blister, as done by many other manufacturers, and should be used for one tooth only and then discarded. It is designed for a maximum of three or four canals in one tooth and should not be sterilised, because the cutting efficiency decreases severely. Practitioners can use their existing endodontic motor with the One Shape instrument. Conclusions: One Shape is optimally designed to prepare the majority of root canal configurations. One Shape is one of the few single file instruments used in continuous clockwise rotation for a quick and probably safe root canal preparation. Parole chiave: continuous rotation, NiTi rotary files, root canal preparation, single file systems