This book is a special-topic publication by the Fatigue and Fracture Reliability Committee FFRC of the American Society of Civil Engineers–Structural Engineering Institute ASCE-SEI . The intent of this book is to report the applications of nondestructive testing NDT methods for fracture-critical structures with an emphasis on the reliability of fatigue assessment. NDT methods have been an important component of structural inspection, especially for detecting critical damages. With nine papers reporting specific case studies, this book is not intended to be a comprehensive coverage of fatigue reliability or NDT methods, but instead provides “practicing engineers with an introduction of NDT methods with immediate applications to real world problems.” This book furnishes a general overview of fatigue reliability and probabilistic methods that gives the audience a concise description of the relationship between NDT and the probabilistic analysis of structural fatigue. The goal of this relationship should result in establishing a “fatigue reliability profile of the structure,” and a “cost-effective scheduling of future repair, retrofit or reconstruction activities” Mohammadi . Although applications of NDT to engineered structures for detecting other damage types are possible, this paper nicely sets the focus of the paper collection, which covers issues about aging aircraft Braun and Mohammadi and civil structures Son and Mohammadi; Mohammadi, Guralnick and Poleppeddi; and Zhao and Halder . Braun and Mohammadi describe fatigue monitoring using a specific assessment methodology and program that includes the permanent placements of sensors motion transducer, temperature gauge, and strain sensors and data recorders on a plane. A data qualityassurance program is established to ensure no error in recorded data. Fatigue reliability is determined from fatigue life projection either by using the Miner-Palmgren damage rule or by the crack growth method. The first-order reliability method is then used to establish fatigue reliability versus flight-hour matrix. For bridge-type structures, Fu and Son et al. review available NDT techniques. Fu differentiates NDT techniques into local and global diagnostic methods, which include liquid penetrant testing, magnetic particle testing, radiographic testing, ultrasonic testing, and acoustic emission testing and visual inspection. Son et al., on