This research program addresses the utilization and control of off-gas produced from in situ oil shale retorting processes. This report summarizes Phase I of the program which focused on off-gas characterization and utilization. Data from relevant experiments were analyzed and typical in-situ off-gas characteristics are defined for the four common retorting inputs: pure air, air/recycle, air/steam, and pure steam. Environmental and economic constraints associated with utilization and control of off-gases from these processes are discussed. Leading technologies available for sulfur removal are summarized. Combustion characteristics of the various off-gases are evaluated. Current technology developments for combustion of ultra-low-Btu fuels are reviewed for application to .i!! situ oil shale off-gas utilization. A new off-gas utilization/control concept involving gas phase fluidized bed combustion is introduced. This process has the potent i alto provide both enhanced combustion and sulfur compound removal within the same vessel. Off-gas utilization power cycles required for commercialization of the in situ processes are defined. For the in situ retorting processes nearest commercialization, those using air/steam input, a detailed power cycle analysis is presented for a 50,000 bbl/day demonstration plant. The analysis first addresses a basic steam cycle expected to be most viable during in-situ oil shale industry development. Then the analysis addresses a gas turbine/waste heat boiler cycle expected to be the prime off-gas utilization option as the industry matures. The system analysis provide performance characteristics and a conceptual design is presented. Areas that require further investigation for the development of off-gas utilization are identified.