Terminology is an integral part of every translation process, necessary to achieve high-quality translation. In the case of EU law, terminology is additionally a matter of legal certainty and clarity. Terminological errors may lead to citizens and companies misunderstanding their rights and obligations, make the harmonization of laws between Member States more difficult and often result in legal disputes at national or EU level, thus tarnishing the image of the European Union and its institutions. This is why EU language services place great emphasis on terminology work and on integrating terminology in their translation process. The aim of terminology work is, firstly, to give translators timely terminological support: to find a correct equivalent, to clear the meaning of a concept, to coin a brand new term or to help them choose the right equivalent in a given context, out of many equally correct terms, based on the criteria of consistency, accuracy and clarity. Secondly, the aim of terminology work is to manage the existing terminology resources. This work is both of a descriptive and prescriptive nature and the central hub for EU terminology is the multilingual termbase IATE, jointly managed by several EU institutions and accessible also to the general public. This chapter describes how the terminology work is done in the Directorate-General for Translation of the European Commission on the example of the practices in the Polish Language Department.