Transesophageal echocardiography is a new method of cardiac imaging with well-defined indications. In view of the absence of hindering anatomical obstacle between the probe and cardiac structures, the images obtained are of high definition, especially as regards the atria and atrial appendages, the mitral, aortic and tricuspid valves and the thoracic aorta. Being easy to perform and little traumatic, this method can be used in ambulatory patients. It is also valuable in intensive care patients and in the peri-operative period. Transesophageal echocardiography is primarily indicated to explore cardiac valve prostheses, notably those of the mitral valve, to identify vegetations and abscesses in infective endocarditis, to detect intra-atrial tumours and thrombi, to evaluate dissections of the aorta, to study the mechanism of mitral regurgitation, to investigate some congenital cardiopathies in adults, such as interatrial septal defects, and to monitor left ventricular function before and after surgery. Owing to its major contribution to the diagnosis of these potentially dangerous diseases, it should soon become a very useful and even indispensable complement of transthoracic exploration in certain cases.