Emergency physicians attending to pediatric patients in acute care settings use electrocardiograms (ECGs) for a variety of reasons, including syncope, chest pain, ingestion, suspected dysrhythmias, and as part of the initial evaluation of suspected congenital heart disease. Thus, it is important for emergency and acute care providers to be familiar with the normal pediatric ECG in addition to common ECG abnormalities seen in the pediatric population. The purpose of this 3-part review will be to review (1) age-related changes in the pediatric ECG, (2) common arrhythmias encountered in the pediatric population, and (3) ECG indicators of structural and congenital heart disease in the pediatric population.