INTRODUCTION: The prevalence of Barrett's oesophagus (BE) is 5 to 6% in the general population, with a progression from dysplasia to adenocarcinoma 0.6 to 0.7 patient-years. Hence, endoscopic surveillance is justified to detect early lesions accessible to endoscopic treatment. However, the relocalisation of lesions detected by biopsies may be difficult during follow-up endoscopies. The purpose of this study was to evaluate the prototype of a magnetic probe for accurate location of the position of the endoscope, allowing the relocalisation of this position in a subsequent endoscopy. We report the results of a feasibility study in pigs and the use of this device in two patients with BE. AIMS & METHODS: The system consists of an electromagnetic (EM) field transmitter and an EM probe constituting the electromagnetic tracking system (EMS) (NDI, Aurora). The EM probe is inserted through the operating channel of a double channel gastroscope. The EM field generator is positionned on the patient chest wall. The system also includes a new software developed at IHU/IRCAD, which performs simultaneous recording of the video from the endoscope alongwith its corresponding position, as measured by the EMS. During a second endoscopy, this software allows automatic synchronization of the recorded video to provide relocalisation of the endoscope in front of previous biopsy sites in the oesophagus. The system was tested in 5 anesthetized pigs. During the first endoscopy, ten markings were performed by argon plasma electrocoagulation (ERBE Tübingen, Germany) in the distal esophagus. The position of each marking was recorded by the system. A second operator to then performed a blind endoscopy on the same pigs and was asked to follow the system implicitly as a guide to relocate the markings. In 2 patients with BE, the system was then tested to facilitate relocalization of the biopsy sites. RESULTS: Ten markings were made in the distal oeosphagus of 5. After withdrawal of the endoscope the second operator found 48 of the 50 markings (96%) using the guidance provided by the system. The positioning of the endoscope provided by the EMS system was within a 2mm range from the initial positionning. In the evaluation of BE patients, the system relocalized the biospy sites within a range of 3mm. CONCLUSION: This preliminary study shows the feasibility of the EMS prototype to relocalize the endoscope in the oesophagus within an acceptable range. The clinical usefulness of this system should be evaluated further during the follow-up of patients with BE.