When it comes to establishing and operating a nationwide personal health record (PHR), effective and efficient terminology management including the development, administration, maintenance and publishing of terminologies is a precondition for semantic interoperability. In the Austrian national patient health record “ELGA” all relevant terminologies are provided and distributed by means of a CTS2-conformant terminology server. In the following article, issues and lessons learned from terminology management in a large-scale eHealth project are presented. Experience has proved the necessity of a national authority for medical terminology management in Austria.