NiTi rotary systems are able to prepare root canals to excellent taper, with less canal transportation, greater preservation of tooth structure, and allow faster canal preparation than hand instruments. Since the capability of NiTi instruments to efficiently enlarge root canals depends on their surface properties, surface treatments of NiTi instruments are examined and the effects of NaOCl, sterilisation processes and electropolishing are discussed. Keywords: autoclave sterilisation, corrosion, NaOCl, NiTi, surface treatment