Abstract: Introduction: The presence of a curve limits the preparation of the root canal and can lead to procedural errors related with the formation of ledges, fracture of instruments, canal transportation or perforation of the apical foramen. Nickel-Titanium instruments are recommended to use in such cases due to their superior flexibility and resistance to cyclic fatigue. Aim: To assess the shaping ability of ProTaper Gold in preparation of moderate curved canals (25º-30º) on extracted human teeth, using x-ray.