The Los Alamos National Laboratory Cray-1 version of the ASPEN code was used to simulate the HYTORT process for retorting eastern oil shale. The model includes 40 unit operation blocks. 5 FORTRAN blocks and 4 design specifications. The retort was modeled using four separate reactor blocks so that the thermal effects of the different reactions in the retort could be analyzed. FORTRAN blocks were used extensively in the retort module to adapt the ASPEN reactor blocks to our model for the retorting reaction chemistry. The HYTORT plant model includes a cold box for recovering H2 from the retort off-gas for recycle and a steam methane reformer unit for producing H2 for the hydrotreater and for retort make-up. The HYTORT plant model was used to perform a process sensitivity study to relate oil and fuel gas production and oxygen consumption to retort temperatures. The HYTORT complex products and the greatest fuel value at a retort temperature of 1500 F, which was the higher temperature considered.