Abstract Effects of irradiation on dislocation recovery kinetics and strengthening have been calculated and compared to reported responses in Fe-2 1 4 Cr-lMo steels. The analysis indicates that predicted interstitial loop growth causes increases in strength at 673 K that are comparable to measure increases in strength at 10 dpa. With increasing temperature, radiation softening was predicted as expected from experimental observations. The transition from hardening to softening was predicted to occur at temperatures about 50 K above the measured transition. A strong hardening effect was predicted from depleted zone accumulation at 673 K, but only when depleted zones were assumed to be unbiased microvoids. Radiation enhanced growth of Mo 2 C precipitates were predicted to have an influence on hardening that was less than predicted for hardening caused by loop growth. At later stages of carbide evolution, irradiation softening may occur because of reduction in solid solution hardening and enhancement in carbide coarsening.