AIM: Childhood leukaemia treatment contains multiple chemotherapeutic agents in high doses that can cause severe toxic effects on heart and other vital organs. In this respect patients taking cancer chemotherapy are followed for these adverse effects. Echocardiographic myocardial performance index (MPI) was reported as a new method of combined systolic and diastolic function for both adults and children, calculated as isovolumic relaxation time plus isovolumic contraction time divided by ejection time. In addition, it has been postulated that increased inter-lead differences in QT interval (QT dispersion) may be associated with an increased risk of cardiac death. The aim of this study was to determine the probable immediate and late adverse effects of childhood leukaemia treatment containing moderate dose of anthracyclines on heart by MPI and corrected QT dispersion (QTcD). METHODS: MPI and QTcD in 55 children with leukaemia and 38 healthy controls matched for age and sex were evaluated. RESULTS: There was no statistically significant difference between MPI values of patients and controls (20.7+/-13.1 (1-59.4) and 16.1+/-13.5 (0.3-77.5), P: 0.1, respectively). Also, there was no significant difference in MPI and QTc values between patients taking active treatment and those who completed the therapy and between the patients given a cumulative dose of anthracycline lower and higher than 250 mg/m2. But QTcD values were found to be higher in patients than controls (0.08+/-0.03 and 0.03+/-0.01, P<0.01, respectively). CONCLUSIONS: There was no overt cardiotoxicity in our children with leukaemia treated with protocols of ALL BFM 95 and TRALL 2000 (Modified BFM in Turkey) containing moderate dose of anthracyclines. However, they can cause subclinical cardiotoxicity and further monitoring and evaluation with such sensitive and noninvasive methods over a longer period of time are needed.