Echocardiograms of 47 children treated with doxorubicin in combination with other cytostatic agents in the period 1979-1984 were reviewed. The authors compared the first and the last echocardiographic registration of every individual patient, analysing the left ventricular dimensions and the shortening fraction which is the indicator of myocardial contractility. Statistical analysis revealed a significant dilation of the left ventricle with a decrease of contractility in the whole group of patients during the therapy. Seven out of 9 patients who had an abnormal shortening fraction at the last measurement died of malignancy. Three children, all in remission of their malignancy, developed a dilated cardiomyopathy that was fatal in two. The possibilities for prevention of this serious complication by means of serial echocardiography during treatment with anthracycline derivatives are discussed.