Transoesophageal echocardiography, initially described in 1976, presently includes M-mode, two-dimensional, pulsed wave, continuous wave, and colour flow Doppler imaging techniques. Although transthoracic and epicardial echocardiography may have utility during some surgical procedures, only the transoesophageal approach provides continuous imaging without interruption of surgery in patients ranging in size from 3 kg to adults. Limitations to its uses include the presence of oesophageal disease or abnormal coagulation. The risk of complications in a large series of conscious or anaesthetized patients is small (less than 0.2%). Examples of its perioperative use in detection of air embolism, delineation of aortic pathology, determination of pericardial tamponade, evaluation of septal integrity, and identification of cardiac chamber contents are described. Critical evaluation of its use to evaluate regional and global biventricular function and native/prosthetic valvular function is provided.