The enormous potential of siRNA as a therapeutic has led to an explosion of interest from the scientific community. There has been intense interest from Big Pharma to capitalise on this new technology but the fact remains that delivery is a key determinant in realizing the full clinical potential of RNA interference. There is an urgent need for better delivery methods to take this technology forward. This book addresses the role of different RNAi molecules in cellular processes as rational for diagnostic and therapeutic approaches. This book will cover RNAi therapeutic design to optimize siRNA potency and reduce off-target effects and current delivery technologies to overcome both intracellular and extracellular barriers. The reader will gain an insight into RNA interference from the cellular mechanisms to screening to siRNA design right through to diagnostic and therapeutic applications.