The saying, "What one does not know, one does not recognize", applies to the interpretation of the electrocardiogram. Recently a wealth of new information on the electrocardiogram has become avail able by correlating electrocardiographic findings with information from new techniques such as His bundle recordings, programmed stimulation of the heart, 24-hour record ing~, and cardiac scintigraphy. Also, our knowledge about the electrocardiogram has been extended by acquiring new epidemiologic data and by follow-up studies on patients with myocardial infarction and bundle branch block. Unfortunately, this new information has to be dug out of several different journals and books. This book brings together this information and ,helps the practicing physi cian in updating his or her knowledge about the 12-lead electrocardiogram as a diagnostic, therapeutic, and prognostic tool. Hein J.1. WELLENS Henri E. KULBERTUS ACKNOWLEDGMENTS Originally, the contents of this book were presented in a workshop on "What is new in electrocardiography?" This workshop was made possible by the generous financial support and assistance of Roussel Nederland. Each of the speakers at the workshop kindly consented to produce a manuscript. We want to express our gratitude to them. The preparation of the workshop, and this book, required a great amount of secretarial assistance: Mrs. Bea Leliveld, Miss Anja Smeets, and Mrs. Thea Niemeyer did this with dedication and efficiency. They surely deserve our thanks. Mr. B.F. Commandeur and Martinus Nijhoff Publishers were responsible for the rapid and expert production of this book.