Knowledge of the course of the mandibular canal and its anatomic variations is of great importance in oral surgery, especially in preprosthetic operations and the insertion of endosteal implants and during the planning of removable dentures prepared in cases involving extensively atrophied mandibles. We review the literature on duplicated mandibular canals, which is based exclusively on radiologic findings. Then, we compare this with an examination of dry mandibles and further radiologic studies. The incidence of duplicated mandibular canals observed in macroscopic examinations of mandibles was substantially higher than that revealed by radiographs. One case involving a novel variation, a triple mandibular canal, is reported.