Durability analysis can be defined as the prediction methodology of safe residual behaviour after a given life time under a complex mechanical loading history in combination with a program of environmental variations. This was, and is a central problem for the reliability of structural components whatever are the basic material systems. With composite systems, combination of different materials in interaction, an integrated material structure design becomes possible. If one of the phases is a polymer, the composite system has time dependent properties and as consequence durability analysis has to be performed taking into account the internal time factor in combination with strong influences from temperature changes and moisture diffusion. Insurance companies need information on durability and reliability in order to cover the risks, and in the event of failure lawyers have to arrive at an agreement om the responsibilites of the different actors involved in the constructiion. This book is an overview of the state of the different aspects of safe structural integrity for a given lifetime of composite structures, with special emphasis on polymer matrix composites. It is of interest for scientists and engineers involved in composites and for designers of composite structural components.