Aim : To evaluate the effect of 3% NaOCland15% EDTA gel on the surface topography of Twisted file NiTi instruments using AFM analysis Methodology :A total of 10 Twisted Files (Sybron Dental Specialties, Orange, CA, USA) .06#25, 23mm were divided into two groups: immersion in 3% NaOCl for 5 min and immersion in 15% EDTA gel for 5 min. Ten surface areas along 3– mm sections at the tip of the files (perfect squares of 2x2 mm) were analysed by AFM operating in contact mode under ambient conditions. Three–dimensional images (200 x 200 lines) were processed using Picoscan version 5.4 system software, and the root mean square value (RMS) of the scanned surface profiles were recorded. Data were analysed statistically. Results :Three–dimensional AFM images of the surface of twisted files of , those immersed in NaOCl and EDTA gel, revealed topographic irregularities at the nanometric scale. RMS values of instruments treated with NaOCl and EDTA solutions were statistically higher than that of the new ones (P < 0.05). Conclusion : Atomic force microscopy three–dimensional images and roughness values indicated that short–term contact between NaOCl and EDTA endodontic irrigants and twisted files instruments caused alterations on the surface of instruments.