Interpretation of pediatric electrocardiograms (ECGs) can be challenging for the Emergency Physician. Part of this difficulty arises from the fact that the normal ECG findings, including rate, rhythm, axis, intervals and morphology, change from the neonatal period through infancy, childhood, and adolescence. These changes occur as a result of the maturation of the myocardium and cardiovascular system with age. Along with these changes, up to 20% of pediatric ECGs obtained in the acute setting may have clinically significant abnormal findings. This article will discuss the approach to the interpretation of ECGs in children, the age-related findings and alterations on the normal pediatric ECG, and those ECG abnormalities associated with pediatric cardiac diseases, including the variety of congenital heart diseases seen in children.