Echocardiographic evaluation of left ventricular (LV) performance was performed in 41 children during and following anthracycline chemotherapy. Prior to treatment LV function was normal in all patients; LV shortening fraction was 35.2 +/- 0.7% and percent of predicted velocity of circumferential fiber shortening was 110 +/- 20%. However, the indices measured concurrent with the final anthracycline dose (mean = 308 +/- 16 mg/sq m) demonstrated a significant decline in LV function. The LV shortening fraction had decreased to 29.5 +/- 0.8% and percent of predicted velocity of circumferential fiber shortening decreased to 94 +/- 4% (P less than .01). Four of the eight patients with evidence of significant LV dysfunction had received thoracic or upper abdominal irradiation. Following cessation of anthracycline therapy, LV function improved within one to six months and had returned to normal in all but two patients, both of whom received irradiation. Echocardiography is useful for the identification of anthracycline-induced LV dysfunction. With discontinuation of further anthracycline administration the functional decline in LV performance appears to be reversible.