Backgrounds: Localization of the esophagus and the left atrium (LA) posterior wall thickness (LAPWT) should be taken into account when delivering radiofrequency energy. Intracardiac echo (ICE) advanced into the LA is useful in visualizing LA and surrounding structure by its high and real-time resolution. Methods: In 73 patients (mean age, 68±12; paroxysmal AF in 45), 3-dimensional (3D) esophagus image was created with CARTO Soundstar® and its location was compared with contrast esophagography saved in Carto UNIVU™. LAPWT adjacent to the esophagus was measured at 4 levels: left superior PV (LSPV), intervenous carina (IC), left inferior PV (LIPV), and LIPV bottom. A target AI value was 260 (25W power) on the esophagus region. Results: All patients had the esophagus posterior to the left PV antrum. Creating 3D esophagus and measurement of LAPWT with ICE was done without any complications. ICE esophagus image was completely overlapped with contrast esophagography. LAPWT (mm) was 2.8 (interquartile range, 2.5-3.2), 2.2 (1.9-2.5), 1.9 (1.8-2.1), and 2.1 (1.9-2.4) for LSPV, IC, LIPV and LIPV bottom, respectively, while LA roof thickness 3.2 (2.9-3.6) (P<0.0001 by ANOVA). No residual conduction gap on the esophagus after the first circumferential PV isolation was found in 64 of 73 (88%) patients. Conclusions: ICE inserted into the LA can reliably locate and display the esophagus and its relationship to the LA. LAPWT was thinnest at LIPV level. AI-guide ablation targeting a relatively low target AI value 260 on the esophagus seemed to be effective.