Adriamycin and daunomycin are highly effective anti-tumor agents but have been known to be cardiotoxic in dosages > 500 mglm'. Echocardiograms were performed in 54 pediatric patients with a variety of malignant diseases in an attempt to detect early evidence of anthracycline-induced cardiac toxicity. Thirty baseline studies were performed while 81 studies were done during and/or following anthracycline chemotherapy. Baseline left ventricular (LV) function was normal; shortening fraction = 34 * 1% and percent heart rate predicted velocity of fiber shortening = 109 ?; 3%. No significant reduction in LV performance occurred until cumulative doses exceeded 250 mg/m2. Between 250 mg/m2 and 450 mg/m2 mean shortening fraction = 30 f 1% (p < 0.025) and percent of predicted shortening velocity = 93 * 4% (p < 0.005). Above 450 mg/m2 a further significant decrease in LV function was noted: shortening fraction = 21 * 3% and percent of predicted shortening velocity = 63 k 10%. Two of the five patients in this group developed congestive heart failure. We currently recommend that echocardiograms be performed prior to the start of anthracycline therapy and repeated every 80 to 120 mg/m2 until a cumulative dose of 250 mg/m2 is reached. Thereafter, echocardiograms should be performed prior to each additional dose. Therapy should be discontinued when shortening fraction < 20% and percent of predicted shortening velocity < 50%. However, selected patients with satisfactory LV performance who have received dosages of 500 mg/m2 may be considered for continued chemotherapy.