success in root canal treatment is achieved after thorough cleaning and shaping followed by complete obturation of the canal system. therefore, endodontic therapy requires specific and complete knowledge of the internal and external dental anatomy, and its variations in presentation. such treatment may be performed in root canal systems that do not comply with the normal anatomical features described in standard textbooks. the internal anatomy of the maxillary central incisor is well known and usually presents one root canal system. this case report describes an endodontic retreatment of a maxillary central incisor with two canal systems.