A study of the cooling effect of secondary fluid injection on the heat transfer between a shrouded rotating disk and a radially inward main flow stream is presented. The investigation is intended as a model study of film-cooled, radial-flow gas turbines. The film-cooling method is reviewed, and the nondimensional parameters governing the heat transfer are obtained. Experimental results, covering the range of radial-flow, gas-turbine operating conditions, were obtained from a film-heated, rotating-disk facility. The heat-transfer behavior of the main stream only was determined separately, and the film-cooling results are presented as ratios of the heat transfer obtained with film cooling to the heat transfer obtained with only the single radial inflow.