The objective has been to acquire the ability to prescribe an efficient process for in situ recovery of a given oil shale resource. The overall efficiency of shale oil recovery processes is determined primarily by a combination sweep efficiency, retorting efficiency and volumetric efficiency. These efficiency components are related to the way in which the retort bed is prepared, the retorting technique employed and the structural characteristics of the mine and in situ retorts. Therefore, the Sandia program addresses these three main areas: bed preparation and characterization; retorting process; and structural stability. For convenience, this report is organized with most of the text under these main headings. However, this separation is somewhat arbitrary and the three areas are not truly independent. The integration of information from the three areas is an integral part of this program.