A one-dimensional mathematical model has been developed for simulating the chemical-physical processes involved in the concurrent, vertical retorting of a rubblized bed of oil shale. Included in the present model are those processes believed to have the greatest effects in either the hot-gas retorting mode or the combustion retorting mode. The physical processes are: axial convective transport of heat, heat transfer between the gas stream and the shale particles, and water evaporation and condensation. The chemical reactions in the shale particles are: decomposition of kerogen and carbonate minerals, reaction of carbon with CO2 and O2, thermal degradation of oil, and release of fixed water. The chemical reactions in the gas stream are: ;combustion of CO produced from the reaction of carbon with CO2, combustion of the fuel components in recycle gas, and oil combustion.