A review of our recent research on the application of suitable transform methods (Laplace and Fourier) to experiments of single-photon decay spectroscopy is presented. These methods are specially advantageous when long lifetimes have to be measured and the fluorescence intensity is low (less than one photoelectron per lifetime). The theoretical part for both transforms, Laplace and Fourier, and the experimental method to corroborate their validity are shown for single exponential decay signals. The theory and computer simulations to extend the applicavility of the Fourier transform to multiexponential fluorescence intensities have also been included.