A principal goal of this book is to provide the reader with the ability to cmpetently analyze a nd co r rectly interpret an ECG. Each of the following chapters addresses this goal. We believe, however, that the reader will be well served by having a compact reference source available when a how-to, step-by-step overview of electrocardiographic interpretation is needed. Chapter 21 is intended to provide this overview. While detailed discussions will be found in chapters preceding chapter 21, tha latter serves as a constantly available reference fo r the reader in need of a memo r y jogger o r a rapid guide. The algo r ithms on the inside front cover serve the same function.