It has long been recognized that attainment of the safety and environmental potential of fusion energy requires the successful development of low activation materials for the first wall, blanket and other high heat flux structural components. Only a limited number of materials potentially possess the physical, mechanical and low activation characteristics required for this application. The current US structural materials research effort is focused on three candidate materials: advanced ferritic steels, vanadium alloys and silicon carbide composites. Recent progress has been made in understanding the response of these materials to neutron irradiation.