Reliability is defined as the ability of a system or component to function under specified settings for a stated period of time. It often plays a crucial role in the cost-effectiveness of a system. The sub-discipline of systems engineering that focuses on the capacity of equipment to function without failure is known as system reliability engineering. It deals with the prediction, prevention and management of high levels of engineering uncertainty and failure risks. Availability, testability, maintainability and maintenance fall under the umbrella of reliability engineering. It focuses on costs of failure resulting from system downtime, cost of spares, repair equipment, personnel and cost of warranty claims. Different approaches, evaluations, methodologies and advanced studies on system reliability have been included in this book. It elucidates the concepts and innovative models around prospective developments with respect to this field. As this field is emerging at a rapid pace, the contents of this book will help the readers understand the modern concepts and applications of the subject.