Several steels representative of recently developed types and having potential for nuclear structural applications were exposed to high energy nuclear radiation, and the resultant properties compared with those of the currently used A212-B and A302-B nuclear reactor pressure vessel steels. Preliminary results from several comparative irradiation experiments indicate that certain higher strength steels, in addition to having initial qualities of higher strength and lower initial ductile-brittle transition temperatures, show smaller embrittlement, earlier embrittlement saturation, and a superior overall response to irradiation at 550 F than that observed for the steels in current reactor pressure vessels.