Chain extended perfluoroether oligomers were found to be miscible with bisphenol epoxy resins at all concentrations. These were evaluated as modifiers for anhydride cured resin systems, taking advantage of the carboxylic acid functionality at the chain ends. By altering the mixing and curing procedure different two-phases morphologies could be obtained varying from fine co-continuous networks, which produced transparent castings, to opaque systems consisting of precipitated heterogeneous particles. While the T-g and flexural modulus were found to be slightly lower than the control cure resin, the addition of the fluoroligomer modifier produced large increases in flexural strength, ductility, and fracture toughness. Samples with an IPN type morphology were found to exhibit an increase in ductility after aging at 200 degrees C for three weeks proportionally to the concentration of fluoroligomer used.