The use of composite materials in engineering components has created a need for a philosophy to support and define the concepts of durability and damage tolerance. That philosophy is often discussed under the general topic of life prediction. The physical behavior that drives the pursuit of this subject is damage accumulation—the various damage modes and failure modes that act and interact to progressively reduce the strength and life of inhomogeneous composite materials with a complex microstructure. In this paper, we will address the issues of defining strength in the presence of widely distributed damage and combining mechanics representations to predict remaining strength (damage tolerance) and life (durability) for engineering components. Examples will be presented, using the MRLife simulation code published by the Materials Response Group for cases in which fiber failure controls the failure of the composite. Finally, we will discuss ongoing efforts to extend the analysis to cases in which matrix-controlled failure is of interest.