Large swelling values associated with a gradual temperature reduction during irradiation have been observed for pressurized tubes irradiated at two initial irradiation temperatures. A comparison of the pressurized tube data with WSA-4 fuel pin cladding swelling data shows that the same behavior is observed in fuel pins subject to temperature changes during irradiation. The fuel pin data cover a large temperature interval, and this information was used to determine temperature and fluence dependencies of the observed enhanced swelling effect. The results show that the enhanced swelling with temperature reductions depends on the initial irradiation temperature, with the maximum value occurring at ∼500°C. The data indicate that the effect saturates with fluence.