The objective of this chapter is to introduce the basics of electrocardiogram. An electrocardiogram is a tracing of the electrical activity that is taking place within the heart. Under normal circumstances, an electrical impulse will travel from the sinoatrial node, spread across the atrium, to the atrioventricular node and through the ventricular septum of the heart. The P wave represents the depolarization of the left and right atrium and also corresponds to atrial contraction. Precordial leads, color code and description of ECG, limb leads in ECG, duration of each wave, ECG changes in myocardial infarction, methods to calculate heart rate in ECG, and ECG interpretation made easy are discussed in the table format.