Several components of power-plants, chemical reactors, and land, air and sea based gas turbines operate at temperatures where creep deformation and fracture is a design concern. Several of these high temperature components, especially those containing thick sections, are subjected to stress and temperature gradients and do not fail by creep rupture. It is more likely that at the end of the predicted creep rupture life, a crack develops at a high stress location that propagates and ultimately causes fracture. Failures can also result from pre-existing defects, in which case the entire life is consumed by crack propagation. Therefore, it is important to develop the capability to predict crack propagation life at elevated temperatures in the presence of creep deformation.The linear-elastic and elastic-plastic fracture mechanics concepts are unable to predict crack growth in the presence of significant creep strains. Thus, this Bulletin will focus on developing the concepts of time-dependent fracture mechanics (TDFM) to account for the role of creep in the crack growth behavior in elevated temperature components. In looking to extend the fracture mechanics concepts to conditions where time-dependent creep deformation is no longer a limitation, we will be taking advantage of considerable analogies that exist between TDFM and the elastic-plastic fracture mechanics (EPFM).