It is rather remarkable that when the cardiac muscle undergoes depolarization and repolarization, these electrical events can be recorded from the body surface; hence the birth of electrocardiography. And this ECG amazingly provides a wealth of clinically useful information as exhibited in this atlas. Thus, ECG is a valuable diagnostic tool that we use in daily clinical practice. Therefore, for quality patient care, it is important that we become proficient in its interpretation. In this atlas, after brief presentations on the basic aspects of ECG, I have compiled typical examples of nearly all ECG entities that we commonly encounter. The primary intent is to help you with pattern recognition, point out salient features, and to help you understand the logic behind the ECG manifestations.