The precipitation behaviour of Type 316 and FV548 austenitic steels irradiated with neutrons in the temperature range 380°–730°C is described and compared with the precipitation behaviour of unirradiated steels. Many of the features exhibited by precipitates formed under irradiation are shown to be very similar to those observed in unirradiated alloys. The similarities improve the understanding of the phenomenon of irradiation induced or enhanced precipitation in austenitic steels.