The mechanical strength of conventional epoxy resins drops dramatically after irradiation to a fast neutron fluence of 1 x 10(22) m(-2) (E>0.1 MeV). Recent results demonstrated that cyanate ester/epoxy blends were not affected at this fluence level. The aim of this study is to investigate the performance potential of these blends at higher fluence levels without significant degradation of their mechanical properties. Short-beam shear as well as static tensile tests were carried out at 77 K prior to and after irradiation to fast neutron fluences of up to 4x10(22) m(-2) (E>0.1 MeV) in the TRIGA reactor at ambient temperature (340 K). In addition, load controlled tension-tension fatigue measurements were performed, in order to simulate the pulsed operation conditions of a tokamak. Initial results show that only a small reduction of the mechanical strength under static and dynamic load is observed at a fast neutron fluence of 2x10(22) m(-2) (E>0.1 MeV). After exposure to 4x10(22) m(-2) (E>0.1 MeV) the interlaminar shear strength of materials with a cyanate ester content of 40% or more is only reduced by 20% to 30%.