Proper chemomechanical disinfection of the entire root canal system is required for a successful treatment outcome. Various techniques of mechanical root canal preparation have been introduced and described. Preservation of the integrity of the root canal anatomy and especially of the location of the apical foramen is important during mechanical root canal preparation. Despite the introduction of flexible nickel–titanium instruments and torque-limited devices, root canal preparation of severely curved canals is still challenging and canals may be transported and/or other procedural errors may occur during preparation procedures. There are several aspects that influence the performance of root canal instruments with respect to their shaping ability. This article elucidates different parameters having an impact on canal transportation and discusses the impact of canal transportation on treatment outcomes.