One of the main objectives of a photokinetic investigation is to determine the absolute values of the reaction parameters. A general standard procedure for such a goal is still lacking in the literature, even though a few methods have been proposed for solving the kinetics of particular reactions, as those reviewed in Chaps. 10 and 16 . In this chapter, a new method is introduced for the elucidation of the photokinetics of any photothermal reaction. It is based on the general model equations proposed in Chap. 19 .