The effect of fast reactor irradiation on the ductility of annealed AISI Type 316 stainless steel is described in terms of strain rate, temperature, and neutron fluence. Creep and tensile data obtained after EBR-II irradiations are presented and analyzed in terms of controlling deformation mechanisms. The basic nature of each deformation process is used to infer ductility loss trends and to define the environmental conditions where specific ductility-fluence relationships apply. The resulting correlation quantitatively describes ductility to fluences approaching 7 × 10²² n/cm², strain rates from 10⁻⁶/h to 10⁴/h, and temperatures from 370 to 760 C (698 to 1400 F).