Numerical simulations were performed to predict the film cooling effectiveness and the associated heat transfer coefficient in a 1-1/2 turbine stage. The leading edge of the rotor blade is film cooled with three rows of film cooling holes. The rotor tip leakage has been investigated for a clearance of 0.8% of blade span. Sliding grid is used for the rotor domain, and interface technique is employed to exchange information between stator and rotor domains. Simulations were carried out for both design and off-design conditions to investigate the effects of the stator-rotor interaction on the film cooling characteristics. The commercial code FLUENT with Reynolds stress model is used in the prediction. It is found that the tilted stagnation line on the rotor leading edge moves from the pressure side to the suction side, and the instantaneous coolant streamlines shift from the suction side to the pressure side with the increasing rotating speed. For the fixed inlet/outlet pressure ratio of turbine stage, the high rpm reduces the heat transfer coefficient on the rotor due to the low rotor relative velocity, and increases the "sweet spot" on the rotor tip. These trends are well supported by the experimental results. (c) 2007 Elsevier Ltd. All rights reserved.