The aim of this study was to describe the acute effects of anthracyclines on left ventricular systolic and diastolic function using different echocardiographic modalities. Thirteen children scheduled to receive anthracyclines were prospectively studied. They underwent complete 2-dimensional and Doppler echocardiographic evaluations, including tissue Doppler imaging, before the first dose and <2 hours after each of the first 3 doses of anthracyclines (dose range 30 to 75 mg/m²). After the first dose, increased end-diastolic wall thickness, decreased wall thickening, and a prolonged myocardial performance index were noted. Parameters of diastolic function changed significantly, with a lower mitral E wave, a decreased E/A ratio, and prolonged isovolumic relaxation time. Also, reduced longitudinal early diastolic myocardial velocity and myocardial velocity acceleration during isovolumic contraction as well as reduced peak longitudinal and radial systolic strain rate and strain were noted. All these parameters remained significantly lower after subsequent doses. After the second dose, significant changes in the shortening fraction and the ejection fraction compared with baseline became apparent. After the third dose, further deterioration in radial peak systolic strain was seen. In conclusion, low to moderate doses of anthracyclines acutely induce cardiac diastolic and systolic dysfunction.