Echocardiography is a new diagnostic technique for noninvasive assessment of the size, structure and function of the heart, using pulsed ultrasound. The physical principles underlying the generation of the ultrasonic signal for diagnostic use and the three modes (A, B and M) of displaying the reflected "echo" signal are briefly discussed. A full echographic study of the heart includes evaluation of the dimensions and patterns of movement of its various structures and chambers. The normal anatomic relations and echographic appearances of these structures and the changes they undergo in some of the more commonly recognized clinical conditions are described. Assessment of output and contractile behaviour of the left ventricle and recognition of various congenital heart defects are two of the more recent applications of this technique. Two-dimensional sector and multiscanning devices permit several areas of the heart to be visualized simultaneously in "real time".