This chapter gives an overview of the CASTOR (CO2, from Capture to Storage) R and D project, funded by the European Union (EU) under the 6th Framework Program. With a partnership involving Industry and Research organizations, CASTOR aims at developing new technologies for post-combustion capture and at studying 4 new European storage sites. The main goal of this project is to develop and validate, in public/private partnerships, all of the innovative technologies needed to capture CO2 at the post-combustion stage and store CO2. The CASTOR R and D target aims to enable the capture and geological storage of 10% of the CO2 emissions of Europe that corresponds to about 30% of CO2 emitted by European power and industrial plants. To achieve this goal, CASTOR would need to improve current techniques and develop, validate, and generalize previously nonexistent methodologies and technologies for the capture of CO2 and its subsequent secure underground storage. © 2005 Elsevier Ltd. All rights reserved.