AbstractThe hydrolytic stability of triglycidyl(4‐aminophenol) (ERL 0500), tetraglycidyl(methylenedianiline) (MY720), and a number of model compounds has been investigated. It has been shown that at 60°C and 96% relative humidity undiluted N‐glycidyl aromatic amine‐based epoxy resins readily undergo hydrolysis followed by homopolymerization. Impurities in the resin may significantly accelerate the rate of reaction. The effect of the consequent loss of epoxide on the performance of an adhesive based on ERL 0500 has been studied. The high‐temperature tensile‐shear strength of Joints was markedly reduced when the adhesive was aged, before cure, for 24 hr at 60°C and 96% relative humidity. Some implications of these findings for aerospace applications of epoxy compounds are discussed.