The costs for carbon dioxide (CO2) capture and storage (CCS) in geologic formations is estimated to be $6-75/t CO2. In the absence of a mandate to reduce greenhouse gas emissions or some other significant incentive for CCS deployment, this cost effectively limits CCS technology deployment to small niche markets and stymies the potential for further technological development through learning by doing until these disincentives for the free venting Of CO2 are in place. By far, the largest current fraction of these costs is capture (including compression and dehydration), commonly estimated at $25-60/t CO2 for power plant applications, followed by CO2 transport and storage, estimated at $0-15/t CO2. Of the storage costs, only a small fraction of the cost will go to accurate geological characterization. These one time costs are probably on the order of $0.1/t CO2 or less as these costs are spread out over the many millions of tons likely to be injected into a field over many decades. Geologic assessments include information central to capacity prediction, risk estimation for the target intervals and development facilities engineering. Since assessment costs are roughly two orders of magnitude smaller than capture costs, and assessment products carry other tangible societal benefits, such as improved accuracy in fossil fuel and ground water reserves estimates, government or joint private-public funding of major assessment initiatives should underpin early policy choices regarding CO2 storage deployment and should serve as a point of entry for policy makers and regulators. Early assessment is also likely to improve the knowledge base upon which the first commercial CCS deployments will rest. (c) 2005 Elsevier Ltd. All rights reserved.