Abstract : This report reviews the state of knowledge of the basic factors that control the durability of epoxies in service environments. The structure-property relations of amine (diethylene triamine, DETA)-cured bisphenol-A-diglycidyl ether (DGEBA) and amine (diaminodiphenyl sulfone, DDS)-cured tetraglycidyl 4,4'diaminodiphenyl methane (TGDDM) epoxies, the effects of sorbed moisture, and the fabrication and environmental factors that control the durability of epoxies are reviewed. The modes of deformation and failure of these materials, which occur primarily by crazing, are controlled by their network structure and microvoid characteristics. The pertinent, basic, physical phenonema induced and/or modified by sorbed moisture that affect the durability of epoxies are reviewed. These include the plasticization, swelling stresses, and modification of the crazing process in epoxies caused by sorbed moisture together with the diffusion characteristics of moisture in these materials. The durability of epoxies in service environments are discussed in terms of the structure-property relations of epoxies, the effect of fabrication and environmental factors and their complex interactions on the formation of permanent damage regions. (Author)