Water requirements and uncontrolled air emissions from well vents and steam generators were estimated for each technology based upon available literature. Estimates of best air emission control technologies were made using data for EOR steam generators actually in use, as well as control technologies presently available but used by other industries. Amounts of solid wastes were calculated for each air emission control technology. Estimates were also made of the heavy metal content of these solid wastes. The study also included environmental residuals which may be expected should coal be used instead of lean crude to produce steam for thermal EOR. It was concluded that from an environmental prospective tertiary oil is preferable in many respects to shale oil, coal and synfuels. Alternative sources of oil such as syncrude, new exploration, and primary production could cause far more environmental damage than incremental EOR. Future EOR in specific regions may be constrained because of environmental issues: air emissions, solid waste disposal, water availability, and aquifer contaminators. Competition for water and the scarcity of surface water or groundwater which are low in total diminutive solids will impede some EOR projects. Risks of groundwater contamination should be minimized particularly because of requirements of the Environmental Protection Agency's new underground injection control program. A quantitative environmental assessment will require a complete and consistent data base for all fields for which EOR is planned out in which tertiary production is taking place. This is particularly true for EOR which will occur in Alaska or in offshore areas, where environments are fragile and where operating conditions are severe. 147 references, 29 figures, 46 tables.