The 10 ton and 150 ton retorts were constructed at the Laramie Energy Technology Center in 1965 and 1969, respectively to simulate the modified in situ oil shale retort. A continuous operation of one or both of these retorts has generated a considerable amount of retorting experimental data. However, no significant effort has been made to identify fundamental parameters controlling the oil yield and retorting rate. Arnold Harak and Leroy Dockter have selected twelve retorting experiments, six with each retort, to show some retorting characteristic comparison between two retorts and tried to develop scale up factors that could be applied to in situ retorting situations. It was indicated in the report that the 10 ton and the 150 ton retorts have somewhat different retorting characteristics.