The effects of irradiation in the Dounreay Fast Reactor and the Dounreay Materials Testing Reactor on the creep-rupture-properties of Type 316 stainless steel tubing were investigated. DFR irradiation produced a loss of rupture ductility but, in general, no change in creep strength in 650 C biaxial tests of solution-treated material. Cold-worked tubes suffered a loss of 550 C creep strength. Irradiation of solution-treated tubes at 650 C in DMTR caused a severe loss of high-temperature ductility and a tenfold reduction of creep rate both during and after irradiation. It is possible that an irradiation-induced carbide precipitation process is responsible for the increase of creep strength.