The authors discuss the value of echorcardiography in cardiac valvular disease. Exploration of the mitral valve gives very precise data concerning diagnosis and evaluation of the degree of mitral stenosis. It may be of value in the diagnosis of certain complications such as intra-atrial thrombosis and gives reliable information in postoperative surveillance. In mitral insufficiency, echocardiography sometimes permits the recognition of certain mechanisms such as rupture of the cordae, ballooning of the lesser cusp and abnormal kinetics in obstructive cardiomyopathy. Exploration of the aortic valve is less informative. Aortic insufficiency gives scarcely any direct signs, whilst echocardiography is of value in aortic stenosis. Ultrasonic study also is useful in surveillance of the kinetics of valvular prostheses. The total absence of risk makes repeated studies possible, rendering echocardiography an essential element in the study of valvular disease.