Doxorubicin and daunorubicin are effective anticancer agents in children, however, their therapeutic value is limited by myocardial cardiotoxicity. In 14 children (median age 5.0 years, range 3-12) prospective studies were performed using pulsed Doppler echocardiography to assess the changes in left ventricular systolic and diastolic filling dynamics. None of these children developed cardiomyopathy. M-mode echocardiographic systolic parameters and Doppler transmitral flow velocities were analysed at baseline, after a cumulative anthracycline dose of 138 +/- 26 mg/m2 (second examination) and after 240 +/- 15 mg/m2 (third examination). At the second examination the acceleration time/ejection time ratio was significantly reduced (P < 0.01), but this was no longer evident at the third examination. There was no significant change of peak velocity over aortic valve, pre-ejection period and change of velocity over time. In contrast, three diastolic parameters changed significantly; the late over early inflow velocity (P < 0.05), mitral valve late time velocity integral (P < 0.01 at the second and P < 0.05 at the third examination) and the ratio A-TVI/TVI (P < 0.025 and P < 0.01). At the third examination the velocity of the A wave was also significantly increased. CONCLUSION In anthracycline treated children left ventricular diastolic function deteriorates before systolic function. Diastolic function parameters should be used rather than systolic parameters to monitor these patients.