This conference proceedings provides the papers presented at the OECD/European Commission joint seminar on Naturalisation and the Socio-Economic Integration of Immigrants and their Children held in October 2010 in Brussels. It takes stock of the current knowledge  regarding the links between host-country nationality and socio-economic integration of immigrants and their children, building on novel evidence on this issue.  It also discusses the role of naturalisation as a tool in the overall framework for immigration and integration policy, with the aim of identifying good practices.