The invention concerns a method of cooling the low-pressure stage of a steam turbine (1) connected into a water/steam loop (12). Coolant (K') flow through parts (24) of the low-pressure stage (2), particularly when idling. In order to ensure particularly effective cooling and to be able also to make use of the heat thus obtained, the condensate (K) from a condensor (4) connected downstream from the steam turbine (1) is used as the coolant (K'), the condensate giving up the heat absorbed during the cooling process to the water/steam loop (12). To this end, the low-pressure stage is connected to a coolant line (22, 22') which is connected to the outlet end of the condensor (4) and which includes a heat exchanger (16, 16') connected into the water/steam loop (12).