In order to provide for best possible child health care, timely access to all relevant medical data is of vital importance. The aim of this study is to investigate the use of unique identifiers, a key instrument in this regard, in the countries of Europe. A survey was carried out in all 28 European Member States plus 2 European Economic Area countries in 2015, and refreshed in 2016. In 23 countries unique identifiers are used to link children's health records. Five countries indicated they currently do not link child health records, and two have no such plans. There is variety as regards the type of number and the issuing process.