The effect of the structure of an epoxy network on the interfacial shear strength of glass epoxy composites is described. Diglycidyl ether of bisphenol-A (DGEBA) cured by using stoichiometric amounts of aromatic diamines [i.e., 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,2＇-bis [4-(4-aminophenoxy) phenyl] propane, 4,4＇-bis(aminophenoxy) benzophenone, bis[4-(4-aminophenoxy)phenyl]sulfone, and 4,4＇-diaminodiphenyl methane] was used as the matrix. Interfacial shear strength, determined by using the fragmentation technique, was found to depend on the polarity of the epoxy network and was highest when DGEBA cured with bis [4-(4-aminophenoxy)phenyl] sulfone was used as the matrix.