[en] Microstructural observations are reported for a series of five commercial ferritic alloys, 2 1/4 Cr-1 Mo, H-11, EM-12, 416, and 430F, covering the composition range 2.25 to 17% chromium, following EBR-II irradiation over the temperature range 400 to 650⁰C and to a maximum fluence of 17.6 x 10²² n/cm² (E > 0.1 MeV). These materials were confirmed to be low void swelling with maximum swelling of 0.63% measured in EM-12 following irradiation at 400⁰C to 14.0 x 10²² n/cm². A wide range of precipitation response was found both as a function of alloy and irradiation temperature. Precipitates observed included M₆C, Mo₂C, Chi, Laves, M₂₃C₆, α' and a low temperature phase as yet unidentified. It is predicted, based on these results, that the major impact of irradiation on the ferritic alloy class will be changes in postirradiation mechanical properties due to precipitation