The effects of secondary material phases added or created in the adhesive bulk during processing; changes in joint material properties due to processing and adhesion (interphase properties) and/or loading, including fatigue loading; and effect of interphase material properties on overlap edge stress concentrations are considered in this paper in relation to the fracture behavior of adhesive joints. A theoretical discussion is provided on each of these issues along with specific examples and experimental and/or calculated data. The experimental data discussed were obtained using bulk specimens (material considerations), independently loaded mixed-mode specimens (ILMMS) (fatigue/fracture considerations), and single fiber fragmentation specimens (interphase considerations and its effect on the overlap edge stress concentration). Cause-effect relations between the above-mentioned fracture issues are highlighted as permitted by the data and the analytical models presented.