This book presents a detailed description of the most common nondestructive testing(NDT) techniques used for the testing and evaluation fiber-reinforced composite structures, during manufacturing and/or in service stages. In order to facilitate the understanding and the utility of the different NDT techniques presented, the book first provides some information regarding the defects and material degradation mechanisms observed in fiber-reinforced composite structures as well as their general description and most probable causes. It is written based on the extensive scientific research and engineering backgrounds of the authors in the NDT and structural health monitoring (SHM) of structural systems from various areas including electrical, mechanical, materials, civil and biomedical engineering. Pursuing a rigorous approach, the book establishes a fundamental framework for the NDT of fiber-reinforced composite structures, while emphasizing on the importance of technique’s spatial resolution, integrated systems analysis and the significance of the influence stemming from the applicability of the NDT and the physical parameters of the test structures in the selection and utilization of adequate NDT techniques.