Surveillance materials consisting of a SA-508 Class 2 forging, a Mn–Mo–Ni Linde 80 submerged-arc weld, and an SA-533, Grade B, Class 1, correlation monitor material were thermally aged on a commercial reactor pressure vessel. The materials were exposed to a thermal environment of 260°C for 209 000 h . This temperature is below the range (minimum of 370°C ) where the effects of long-term thermal aging are typically considered relevant. Charpy impact, master curve transition temperature, upper-shelf fracture toughness, and tensile testing were conducted to evaluate the long-term thermal aging changes in material properties. Small changes in the impact properties were observed for all the materials, but were generally within the 95 % confidence bounds for typical Charpy data. Upper-shelf energy also showed small variations, but a general decrease for all materials was not seen. Fracture toughness testing at the upper shelf indicated that the upper-shelf toughness had increased, however the data is scattered. Master curve T0 testing in the transition region showed little change in the forging and plate results; however an improvement in the transition temperature of the weld metal was measured.