A virtual reconstruction of the geometry of the esophagus was produced using an electroanatomical mapping system and a specially designed catheter in 20 consecutive patients undergoing circumferential pulmonary vein isolation. The course of the esophagus, its motion and its proximity to the predicted lines of application of radiofrequency energy to the left atrium were evaluated. Thirteen (65%) were located centrally (i.e. >10 mm from the ostium), 69 (30%) laterally (i.e. <10 mm from the ostium) and 1 (5%) obliquely. No movements larger than 10 mm occurred during the procedure. Conventionally, the radiofrequency ablation lines are configured such that, in 50% of patients, radiofrequency energy is applied to areas adjacent to the esophagus. In order to decrease the potential risk associated with this procedure, either the position of the ablation lines was altered to bring them closer to the ostium (by 15%) or the power was reduced (by 35%). Although there was no significant movement of the esophagus during the ablation procedure, its course was variable. Consequently, the ablation strategy was altered in a substantial number of cases.