This thesis reports the results of a mathematical investigation of the underlying principles that govern the experimental performance of an oil shale retort. Such an investigation naturally separates into 2 principal areas:a study of the kinetics of oil shale pyrolysis and a study of the retorting combustion process. A system of thermal decompositions is presented that provides a description of the mechanism of oil-shale pyrolysis. Specific rate constants for systems of thermal decompositions studied are estimated by a least squares procedure. The estimates thus obtained provide a mathematical model of the corresponding thermal decomposition system. A model that generates a good fit to experimental data, in comparison with other models studied, is based on a thermal decomposition system consisting of 2 first-order reactions and 3 second-order reactions. Values computed for the specific rate constants corresponding to that system are shown to exhibit a temperature dependence that is in good agreement with the Arrhenius equation, over the temperature range of the data used in the study.