In the first section a description of the process zone (the cause of the slow crack growth) is presented, along with a literature review of work performed to understand the effect of this nonlinear zone. Recent models used to theoretically and experimentally predict the size and effect of the process zone are explained in detail in the second section. A model is presented to predict Mixed Mode fracture in materials which exhibit slow crack growth. This model is an extension of the model developed by one of the authors to predict Mode-I fracture. Understanding Mixed Mode crack propagation is necessary to solve many structural engineering problems, and an example of such a problem is given in the last two sections.