The kinetics of heterogenous systems such as semiconductor electrodes, colloidal particles, oxide surfaces, and the fluorescence of dyes bound in polymer matrices or to biological membranes often give curved semilogarithmic plots when tested for first order kinetics. However, the kinetics are not of a higher order, e.g., second, because when normalized by the initial concentration, the decay curves all lie on a common curve. It is common practice to fit such curves to a multiexplonential expression. This book presents an alternative general model, in which there is a Gaussian distribution of the logarithm of the rate constant about some mean and which introduces only one additional parameter - the width of the distribution. Data from the kinetics of semiconductors surface states, of colloidal semiconductor particles, of surface oxides, of the fluorescene decay of a dye bound to biological membrane, and the dynamics light scattering experiments are shown to fit the model. In the case of the colloidal semiconductor particles, there is good agreement for the radial dispersion between the value found from dynamic light scattering and the value found from analysis of the kinetics.