Tension specimens of four basic stainless steels having a body-centered cubic (bcc) or face-centered cubic (fcc) structure without or with nickel addition have been fabricated by casting and by powder metallurgy (without and with TiO² addition). These specimens have been irradiated at 60 C (140 F) up to a 1.6 × 10²² n/cm² fast fluence (> 0.1 MeV) and ruptured at 700 C (1292 F). A structural and statistical analysis shows that bcc structure, powder metallurgy fabrication methods, TiO² additions, and transgranular rupture enhance the 700 C resistance to fast neutron embrittlement. The degree of embrittlement is related to the rupture mode before irradiation.