Advances in experimental research in the United States toward an improved understanding of property changes in steel by elevated temperature (∼288°C) irradiation are summarized. Four areas of investigation are reviewed, including the confirmation and demonstration of guidelines for radiation-resistant steels, the isolation of metallurgical factors contributing to variable radiation embrittlement sensitivity, the qualification of in situ heat treatments for periodic vessel embrittlement relief, and the correlation of notch ductility and fracture toughness changes with irradiation. Overall, the current state of the art provides both a high capability for tailoring steels for radiation service in new vessel construction and a promising method for controlling radiation embrittlement buildup in existing vessel construction.