Abstract: A gas turbine is provided wherein the thermal stresses in the turbine rotor are reduced. The rotor includes a central disc with a peripheral rim, and a plurality of blades extending radially outwardly from the rim, and to reduce thermal stresses, a duct arrangement is provided which selectively directs hot gases from the turbine combustor to the rim during the turbine start-up. The hot gases from the combustor serve to heat the rim, and thus decease the start-up period necessary to bring the temperature profile of the rotor into the operating temperature range. After the start-up period, the duct arrangement is then used to direct cool gases from the turbine compressor to the rim of the rotor in order to maintain a lower rotor equilibrium temperature.