Abstract A major contributor to increased atmospheric CO 2 levels is fossil fuel combustion. Roughly one third of the carbon emissions in the United States comes from power plants. Since electric generation is expected to grow and fossil fuels will continue to be the dominant fuel source, there is growing recognition that the energy industry can be part of the solution to reducing greenhouse gas emissions by capturing and permanently sequestering CO 2. Consequently, an important component of the United States Department of Energy’s (DOE) research and development program is dedicated to reducing CO 2 emissions from power plants by developing technologies for capturing CO 2 and for subsequent utilization and/or sequestration. Injection of CO 2 into geologic formations is being practiced today by the petroleum industry for enhanced oil recovery, but it is not yet possible to predict with confidence storage volumes, formation integrity and permanence over long time periods. Many important issues dealing with geologic storage, monitoring and verification of fluids (including CO 2) in underground oil and gas reservoirs, coal beds and saline formations must be addressed. Field demonstrations are needed to confirm practical considerations, such as economics, safety, stability, permanence and public acceptance. This paper presents an overview of DOE’s research program in the area of CO 2 sequestration and storage in geologic formations and specifically addresses the status of new knowledge, improved tools and enhanced technology for cost optimization, monitoring, modeling and capacity estimation. This paper also highlights those fundamental and applied studies, including field tests, sponsored by DOE that are measuring the degree to which CO 2 can be injected and remain safely and permanently sequestered in geologic formations while concurrently assuring no adverse long term ecological impacts.