ICD therapy has become the standard form of treatment for ventricular tachyarrhythmias. With clinical data showing its efficacy in both secondary and primary prevention of premature sudden death, its use is likely to increase dramatically in the next decade. Technological advancement has been instrumental in simplifying ICD implantation. However, technical additions to the device have also made its scope of functions more complex. In addition to providing rapid and effective therapy for ventricular tachycardia and fibrillation, the ICD is now capable of providing a full spectrum dual-chamber pacing as well as therapies for atrial fibrillation. Soon, it will also be able to provide treatment for congestive heart failure using multi-site ventricular pacing and provide continuous hemodynamic monitoring. This book serves as an introductory text to those who are relatively new to this technology. In its manual form, it outlines the pertinent components of ICD functions and the basic differences among the various models. It provides practical points in ICD implantation, and in its programming and trouble-shooting.