The anthracycline antibiotics, daunorubicin, doxorubicin, and the newer derivatives, are important components of many antineoplastic chemotherapeutic regimens. Their usefulness is limited by their cardiotoxicity. Sequential monitoring of cardiac function of patients undergoing chemotherapy allows identification of subclinical cardiotoxicity. In many patients monitoring can thus guide the modification of the chemotherapy to minimize cumulative cardiotoxicity, reducing acute and long-term clinical and subclinical sequelae. Such monitoring also aids in the comparison of cardiotoxicity produced by different drugs and different methods and schedules of drug administration. The considerable variability of monitoring regimens between institutions and in the literature has detracted from its usefulness. The Cardiology Committee of the Childrens Cancer Study Group has, therefore, reviewed the field and has formulated recommendations for standardized noninvasive monitoring of children during and immediately after chemotherapy and for the modification of the chemotherapy where indicated.