Instrument fracture is a serious concern in endodontic treatment. Several studies have evaluated the influence of various factors on the fracture of nickel-titanium endodontic rotary instruments. The present study analyzes the influence of electrochemical polishing on flexural fatigue and torsional properties of K3 nickel-titanium endodontic rotary instruments. New files and polished files were tested for flexural fatigue and for resistance to fracture by twisting. The t test was used to compare the groups for number of cycles, angle of rotation, and maximum torque necessary to fracture. No statistical difference existed between these groups. Scanning electron microscopy analysis showed no significant differences caused by electrochemical polishing between these groups. These results suggest that electrochemical polishing has no influence on resistance to fracture of K3 rotary instruments.