Additive manufacturing (AM) is a novel fabrication process with the potential to create unique parts beyond the capabilities of conventional manufacturing methods. However, because the AM process produces both the part and the material simultaneously, certification of safety-critical structural metallic parts requires new approaches that more explicitly quantify the influence of the AM process on the quality of the part. For example, the AM process can, when not properly designed and controlled, create defects, such as porosity, lack of fusion, or severe surface roughness. If these defects occur in a region of significant cyclic stress, they can promote the nucleation of cracks that, in turn, can grow to cause fracture of the part. This paper summarizes recent investigations into analytical characterization of defects and their effect on the structural integrity of additive manufactured parts. Specifically, this work documents predictive mechanics models that characterize the effects of pores on fatigue crack formation. These results provide insight into the effects of pore size and shape on fatigue lives under uniaxial tension.