Instrument fracture complicates the endodontic procedure by obstructing debridement, delaying treatment completion and affecting the patient's dental experience. When a file fractures there are several treatment options that could be selected, however, the future management should be based on the effect of the fractured instrument on treatment outcome. The aim of the following review was to analyse the literature assessing the impact of endodontic instrument fracture, focusing on its influence on endodontic prognosis and treatment outcome. A comprehensive MEDLINE search including various keywords identified several publications that considered the variables. Analysis of the publications highlighted a paucity of quality long-term clinical outcome studies relating specifically to the influence of instrument fracture. The available studies demonstrated a wide variety of methodologies reporting conflicting findings; therefore, meaningful conclusions were difficult. Within the confines of the literature it appears that retained fractured instruments do not reduce the prognosis of endodontically treated teeth if apical periodontitis is absent, however, if disease is present healing is significantly reduced. Therefore, the stage at which an instrument fractures in infected cases appears likely to be significant as canal disinfection will be compromised accordingly. Considering the risks associated with file removal, perhaps this should only be attempted if apical disease is present. Although it is accepted that the nature of file fracture precludes integration into randomised prospective trials, there is a need for well designed long-term outcome studies investigating the influence of fractured files.