Iron-based austenitic alloys are often observed to develop magnetic properties during irradiation, possibly associated with the radiation-induced acceleration of ferrite phase formation. Some of the parametric sensitivities of this phenomenon have been addressed using a series of alloys irradiated in the BOR-60 reactor at 593 K. An increase in magnetic phase amount for all alloys was observed over the 0–12 dpa dose range. However, magnetic phase (ferrite according to TEM results) did not appear to continuously increase at higher doses (above 12 dpa) but did tend to saturate. The formation of a magnetic phase in austenitic stainless steels during irradiation at 593 K appeared to be sensitive to alloy composition. It was found that silicon and manganese accelerated ferrite accumulation in the dose range of 0–12 dpa, whereas carbon and probably molybdenum resisted it. Also, an increase in grain size resisted ferrite formation, but cold work was found to stimulate it.