The heart was evaluated by echocardiography in 56 patients at risk for myocardial iron deposition. Fifty-four had congenital anemia for which they required repeated transfusions, and two had primary hemochromatosis. The data, plotted according to one of three functions of the body surface area, were compared to values obtained in 105 normal subjects whose age spanned a similar range. Left ventricular wall thickness, transverse dimension and mass, as well as left atrial transverse dimension, were increased in the majority of patients with chronic iron overload despite the infrequent occurrence of cardiac enlargement on routine chest films (32 per cent) or electrocardiographic abnormality (16 per cent). Left ventricular ejection fraction was normal in all but four patients. These four patients died within a six month follow-up period suggesting that deterioration in systolic function is an indicator of poor prognosis. Our findings indicate that echocardiography provides a simple noninvasive means for assessing changes in cardiac structure and function that should prove useful in the serial evaluation of patients who are at risk for the development of myocardial iron deposition.