The aim of this volume is to present to researchers and engineers working on problems concerned with the mechanics of solids and structures, the current state of the development and application to procedures for assessing the reliability of a system. Particular attention is paid to their use in the analysis of complex engineering systems. The topics covered reflect the need to integrate, within the overall methodology, statistical methods for dealing with uncertain parameters and random excitation with the development of a suitable safety indexes and design codes. The basic principles of reliability theory, together with current standard methodology, including a consideration of the operational, economic and legal aspects of reliability assurance, is reviewed, together with an introduction to new developments, such as the application of expert systems technology. Damage accumulation predictions, with applications in seismic engineering are also covered.