The history of electric cardiac stimulation is long and fascinating. The grow- ing clinical importance has been recognized and renewed as Zoll in 1952 described a successful resusciation in cardiac standstill by external stimula- tion. Meanwhile, patients with disorders of cardiac rhythm have been treated all over the world for about 15 years. Recently the technical refinements of intracardiac stimulation in combination with a subtile analysis of endocavi- tary electrocardiograms improv d the understanding of human intracardiac conduction. These new procedures include the possibility to study the initia- tion and termination of tachycardias. - The pertinent interest in these devel- opments and the intention to learn more about the basic fundamentals of excitability and conduction under both normal and pathological circum- stances were reasons to organize an international symposium on that topic. - The papers contained in this book were presented at this meeting on diagnos- tic and therapeutical tools of cardiac pacing, held at Munich on November 7 and 8, 1975, sponsored by the first Medical Clinic of the University of Munich and generously supported by Medtronic. Especially focused are the investigations on sinus node function, disturbances of av-conduction and electrophysiology of supraventricular and ventricular tachycardias. The content of the book that is emerging from the symposium were created by the authors. I wish to thank them for teaching us about the recent advances in cardiac tissue stimulation by electricity. Much credit is due Priv. Doz. Dr. B. Uideritz, who organized the symposium and published these proceedings.