The irradiation temperature and fluence dependences of precipitates formed in Type 316 stainless steels with and without titanium have been studied for specimens irradiated over a fluence range of 3 × 10²⁶ to 25 × 10²⁶ n/m² (E > 0.1 MeV) and a temperature range of 370 to 730°C. A precipitate formation diagram using irradiation temperature and fluence as the two coordinates is constructed. The composition of M⁶C is found to be irradiation temperature dependent. The composition of Laves is found to be both irradiation temperature and fluence dependent. The variable composition behavior of the precipitates, M⁶C and Laves, during irradiation is discussed in terms of nonequilibrium segregation and the radiation-induced off-stoichiometric characteristics of the precipitates.