Properly conducted endodontic therapy ensures that the tooth function is preserved and kept which would otherwise be lost. Pre-conditions for a successful endodontic therapy are: to make a good diagnosis , good quality and clear x-ray without which no endodontic thera-py should be started, correct trepanation hole and linear access to canals, correct choice of instruments and work techniques in order to prevent complications such as ledge forming or creating an artificial canal. Procedural accidents that could not be predicted or prevented occur in a small percentage even when you work properly, leading to the failure of a thera-py. It is necessary to spot them on time and repair adequately. Fractured instruments in the root canal are a real challenge for the clinician. They can be removed, bypassed or the canal can be processed and filled up to the position of the fractured instrument. The procedure is similar to the one which is applied when a ledge appears in the canal. The fractured instru-ment is bridged with steel instruments #6, #8 and #10 and one should try to achieve the original working length. Before the fractured instrument is extracted the canal has to be prepared and the proper coronal access to the fractured instrument ensured. This can be achieved using diamond drills of various lengths and diameters.(26) After that ultrasonic canal instruments, extirpators or Hedstrom files, ultrasonic instruments or various specialized sets for extraction of instruments are used (Masseran set). If none of the mentioned techniques has given results, the canal coronary to the fractured fragment is instrumented and filled. In order to prevent fracture of instruments in the root canal it is necessary to knnow physical and mechanical properties and to limit the use of force. One should also check the used in-struments regularly and discard the damaged ones. It is also necessary to lubricate the root canal constantly during cleaning and treatment in order to prevent friction, heating and the overload of instruments. The treatment prognosis with such procedural accidents depends on the time when the frac-ture happened and the grade of canal infection.