The constitutive equations for creep, swelling, and damage under irradiation are discussed in terms of incorporating the transient behavior of swelling after the incubation fluence as well as the effect of transient creep. Creep during irradiation is assumed to consist of irradiation-induced creep and irradiation-affected thermal creep, and the dilatational part of irradiation-induced creep is identified with swelling. The irradiation-induced creep is formulated by postulating the stress-induced preferential absorption mechanism. Then, the continuous transition of swelling after the incubation fluence is formulated using the curvature parameter of Bates and Korenko. For transient creep, on the other hand, the McVetty creep law and the Kachanov-Rabotnov creep damage theory are modified to describe irradiation-affected thermal creep. The resulting equations are applied to predict creep before, during, and after irradiation of 20% cold-worked Type 316 stainless steel at elevated temperatures, and the validity of the equations is discussed by comparison with experiments. Finally, the bulging and rupture process in fast breeder reactor fuel cladding is analyzed using the equations.