One route to improving the photographic properties of PTG imaging materials and further the basic understanding of their photophysics is to better quantify the quantum yield of sensitization. A method was developed to estimate the absolute quantum yield of sensitization for IR-sensitive PTG imaging materials. The method utilizes three techniques: sensitometry, photobleach, and Monte Carlo simulation. Sensitometry and Monte Carlo simulation are well-known techniques. The photobleach technique is an optical technique developed to measure the absorptance of the dye adsorbed to the silver halide grains. The absorptance spectrum, by itself, is not sufficient because the absorption peak for dye adsorbed to silver halide and the absorption peak of dye not adsorbed to silver halide are not sufficiently shifted in position to allow us to resolve them. The photobleach technique is based on the discovery that the dye effectively adsorbed to the silver halide photobleaches much more readily. Using this distinction, the absorptance of the dye adsorbed effectively to the silver halide grains was extracted. The mean number of absorbed photons required to form a latent image was estimated to be 35 ± 7 for the PTG samples studied. In addition, practical applications of these techniques are discussed.