THIS MANUAL IS INTENDED to provide a background for developing elastic-plastic fracture toughness data in accordance with ASTM Test Method for J-Integral Characterization of Fracture Toughness (E 1737) and ASTM Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement (E 1290). These standards provide the requirements for obtaining J-integral and CTOD quantities from laboratory tests; however, they provide little information on why certain requirements are imposed and how to carry out various aspects of the tests.