The European Commission (EC) and the OECD Nuclear Energy Agency (NEA) have, over the past several years, sponsored a project on the engineered barrier system (EBS) used in geological disposal of long-lived radioactive wastes. The EC/NEA EBS Project has examined how to design, characterise, model and assess the performance of engineered barrier systems, and how to integrate these aspects within the safety case for geological disposal of long-lived radioactive wastes. This report provides a synthesis of the EBS Project, and summarises its main results and findings.