The European HTR R&D project ARCHER (Advanced High-Temperature Reactors for Cogeneration of Heat and Electricity R&D) builds on a solid HTR technology foundation in Europe, established through former national UK and German HTR programs and in European framework programs. ARCHER runs from 2011 to2015 and targets selected HTR R&D subjects that would specifically support demonstration, with a focus on experimental effort. In line with the R&D and deployment strategy of the European Sustainable Nuclear Energy Technology Platform (SNETP) ARCHER contributes to maintaining, strengthening and expanding the HTR knowledge base in Europe to lay the foundations for demonstration of nuclear cogeneration with HTR systems.The project consortium encompasses conventional and nuclear industry, utilities, Technical Support Organizations, R&D organizations and academia. ARCHER shares results with international partners in the Generation IV International Forum and collaborates directly with related projects in the US, China,Japan, the Republic of Korea and South Africa. The ARCHER project has finished, and the paper comprises an overview of the achievements of the project. ; JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparedness