The state-of-the-art of environmental research of injected enhanced oil recovery (EOR) and/or waste fluids is presented with respect to (1) interactions and compatibilities with reservoir fluids and rocks, and (2) their long-term environmental fate. Major environmental impacts associated with EOR are: (1) possible contamination of surface and groundwater, and (2) possible contamination of land. Although the report focuses on EOR fluids, many other liquid wastes also are considered. When EOR chemicals and/or waste fluids are injected into deep wells for oil recovery or disposal, they may pose environmental problems unless the injection process, oil recovery process, or waste disposal process is carefully planned and executed. This report discusses injection waters, water compatibilities, formation rocks with emphasis on clay minerals, corrosion, bacterial problems, EOR operations, waste fluid injection operations, injection well design, radioactive wastes, transport and fate processes, and mathematical models. 206 refs., 9 figs., 4 tabs.