Management of difficult and complex cases–a real challenge for every endodontist. Ignoring and incompetence to manage complex cases, can lead to instrumentation errors–ledges, zipping, blockages, perforations or instrument fracture, that may compromise the outcome of treatment. The rational approach is the key to success. From planning to performing, every step of treatment must be argued and well determined. Knowing the anatomy and to be able to read the preop radiological investigations, move us to phase of instrumentation, where our knowledge and ability to select the right technique, instruments, and sequence of files, make us have an absolute control and predictability on extreme difficulty clinical cases.