Echocardiography is a valuable technique for the diagnosis and serial follow-up of patients with impaired cardiac function. It is subject to certain limitations due to the assumptions inherent in deriving ventricular volume from a one-dimensional measurement and must be interpreted with caution in cases of suspected regional abnormalities of contraction. Given these caveats, echocardiography is valuable in the quantitative assessment of cardiac size and the level of compensation in patients with primary myocardial disease, valvular heart disease, and left ventricular hypertrophy. It can detect abnormal contraction in some patients with ischemic heart disease and provides an accurate method to serially follow changes produced as a result of drug or surgical therapy. Finally, two-dimensional techniques promise to provide a new perspective on the evaluation of patients with regional wall motion abnormalities.