Abstract : In the last twenty years, much progress has been made with the continuum mechanics characterization of crack growth rates through the application of linear elastic and elastic-plastic fracture mechanics, and such analyses are now in widespread use for defect-tolerant design codes. Similarly, an understanding of the role of microstructure in improving the resistance to fracture and fatigue has emerged to the point where alloy design guidelines exist for the production of alloys with optimum resistance to fatigue failure. However, much work remains in the definition of mechanisms associated with environmentally-influenced crack growth, with the effect of variable amplitude loading, with the problem of the short flaw, and in the fracture of microscopic structures (e.g., packaging problems in the electronics industry).