The principal objective in the mathematical analysis presented was to describe mathematically the oil yield, the amounts of oil degradation into coke and gas, and the rate of oil generation in the retorting of oil shale at various pressures. The results of the analysis are in good agreement with the experimental results obtaine under various retorting conditions. In this analysis, the rate equations for the decomposition of organic matter the recovery of liquid oil as oil mist or oil vapor, and the stoichiometry factors were determined from the experimental data on powdered oil shale with nitrogen as a sweep gas.