Purpose: We aimed to prospectively interpret the cardiac repolarization changes with 12-lead electrocardiography(ECG) in children with cancer who were treated with anthracycline drugs.Materials and methods: A total of 53 patients with cancer treated with anthracycline were enrolled in the study.During 6-month follow-up, standard 12-lead ECG was performed at basal, 1st, 4th, and 24th hours after thefirst dose of anthracycline treatment, at the time of 120 mg/m2 cumulative anthracycline dose and 240 mg/m2of cumulative anthracycline dose in the same patients, respectively. P dispersion (PWd), QT dispersion (QTd),corrected QT dispersion (QTcd), Tp-e interval, Tp-e/QT, and Tp-e/QTc ratio were obtained from 12-lead ECG.The patients were classified into three groups according to increasing cumulative anthracycline doses: Group 1:first dose (n=53), Group 2: 120 mg/m2 (n=53), Group 3: 240 mg/m2 (n=53).Results: The median age was 48 months (range 9-192 months). While PWd, QTd, QTcd, and Tp-e interval weresignificantly increased during first 24 hours of the first dose (p<0.001, p=0.005, p=0.041, p=0.016, respectively),Tp-e/QT and Tp-e/QTc ratios were significantly altered during first 24 hours of 120 mg/m2 cumulative dose ofanthracycline treatment (p<0.001). Any changes in 12-lead ECG were not significantly at 240 mg/m2 cumulativedose. However, it was detected that all variables were affected according to each increased anthracyclinecumulative dose despite it was not statistically significant.Conclusions: ECG parameters such as PWd, QTd, QTcd, Tp-e interval, Tp-e/QT, and Tp-e/QTc ratios areuseful for detecting subclinical cardiac abnormality and acute anthracycline toxicity during both uses of singledose anthracycline and increased anthracycline doses. These parameters may also predict arrhythmias inpatients with cancer.