Endodontic retreatment using Canal Finder K files and chloroform was performed in 106 gutta-percha-obturated, curved root canals, 71 in vitro and 35 in vivo. The minimum time taken to bypass the obturation in a single root canal was 3 s and the maximum time 95 s. The mean times were 19 and 27 s in the two in vitro groups and 32 s in the in vivo group. Eighty-nine percent of the root canals which had been obturated short were bypassed apically in vivo. Root canal curvature was well maintained in all but two root canals. In these two cases apical transportation occurred. Breakage of files occurred three times in vitro, but this did not prevent the completion of bypassing with new files. These results are attributed to the mode of action of the Canal Finder system, which makes it an efficient root canal pathfinder. The advantages of the suggested technique are discussed in light of the clinical considerations of endodontic retreatment.