Twin Registries: An Ongoing Success Story

In the mid-1990s a German funding agency rejected a grant application for a twin heritability and linkage study on the grounds that 'twin studies were an outdated methodology with no scientific merit, publishable only in obscure journals if anything …'.Neither Twin Research and Human Genetics nor any of the other peer-reviewed journals cited by the authors of this special issue warrants the term 'obscure'.Rather than being 'outdated', twin research has proven its increasing value for studying the complex interplay of genes and environment in humans; PubMed lists 713 entries for 'twins ' for 1990, this number increasing to 723, 979 and 1126 in 1995, 2000 and 2005, respectively.One of the fundamental requirements for twin studies is access to twins, and twin registries, rather than spontaneous recruitment on a 'per study' basis, is the way to achieve this.In 2002 this journal devoted a full special issue to this topic, and established as well as newly emerging twin registries presented their recruitment strategies, phenotyping focus and their visions for future research and collaborations.The purpose of that issue was not just to serve as a directory of registries but was to encourage others to start or extend twin collections without having to 'reinvent the wheel'.Since 2002, significant progress has been made around the globe.New twin registries have emerged in countries including Chile, Israel, Spain, and