Doxorubicin is the most frequently used anthracycline antibiotic that expresses significant toxicity. Among all side  effects, hematological are the most common, while cardiac side effects are the most serious and the most important. The aim of this study was to investigate whether doxorubicin containing combined chemotherapy used in treatment of childhood acute lymphoblastic leukemia (ALL), influences electrical activity of the myocardium and left ventricular function in affected children. Experimental group consisted of 20 children with newly diagnosed ALL treated according to protocol YU ALL 95, while the control group consisted of 20 healthy children. Electrocardiograms (ECG) at rest were taken and analyzed, and corrected QT intervals (QTc) calculated. All children had echocardiograms (ECHO) including fractional shortening (FS) and ejection fraction (EF). Electrocardiograms, FS and EF were normal in all subjects, and were similar in both groups.