OBJECTIVE : To assess the correlation between left atrial measurements using 2- and 3-dimensional transesophageal echocardiography. METHODS : Prospective, observational study. METHODS : Single, tertiary care, academic medical center. METHODS : The study comprised 63 consecutive patients undergoing cardiac surgery with cardiopulmonary bypass and intraoperative transesophageal echocardiography. METHODS : In addition to the standard comprehensive intraoperative transesophageal examination, study images were obtained by designated anesthesiologists from the study team. RESULTS : The 2-dimensional transesophageal echocardiography views included 4-chamber, 2-chamber, aortic valve short axis, and aortic valve long axis. For the 3-dimensional images, full-volume (90 × 90) data sets were acquired from 4-chamber and aortic valve short-axis views over 4 beats with apnea. Left atrial height, mediolateral length, anteroposterior length, and area were measured in 2- and 3-dimensional images. Left atrial length in the short- and long-axis views of the aortic valve also were measured in 2- and 3-dimensional images. Results indicate that for all patients in this study, the 2- and 3-dimensional measurements correlate well and the 2 observers were in agreement with each other. CONCLUSIONS : Two- and 3-dimensional measurements of the left atrium correlated well. Measurements made using 3-dimensional transesophageal echocardiography were subject to similar limitations as those made using 2-dimensional echocardiography. The benefits of 3-dimensional transesophageal echocardiography and multiplanar reconstruction could be expanded by improvements in ultrasound technology and software.