This article explains the necessity of epoxy hybridization and then focuses on the use of polyurethane elastomers to modify epoxy resin adhesives. The various approaches that have been employed in the past are reviewed and the resulting properties and applications are identified. Epoxy resins with their versatile properties have found a unique position in the adhesives industry. About 30% of the total epoxy resin production is consumed as adhesives in a wide range of structural applications. Epoxy resin adhesives provide shear strength on almost all surfaces except some nonpolar substrates. The main disadvantage with epoxy adhesives is that they are very rigid if left unmodified. This rigidity results in lower impact resistance and peel strength than required for some applications. One way of modifying epoxy adhesives systems to provide greater toughness is to blend or co-react the epoxy with a more flexible elastomer such as polyurethane.