The EEA Agreement explicitly states that a country which becomes a member of the EU shall also apply to become party to the EEA Agreement (Article 128). The terms and conditions for such a country to participate in the EEA Agreement shall be subject to an agreement.
With ten new members acceding to the EU on 1 May 2004, there was a need to negotiate and adapt the EEA Agreement to take account of the new situation. This was the first time in the ten-year history of the EEA that new members needed to accede to the Agreement following negotiations on the terms of participation. The resulting EEA Enlargement Agreement was provisionally applicable as of 1 May 2004, concurrently with the EU Enlargement, and entered into force on 6 December 2005 after the completion of ratification by all Parties.
On 1 January 2007, Bulgaria and Romania joined the EU and the corresponding EEA Enlargement Agreement extending the EEA to those countries was provisionally applicable as of 1 August 2007 and entered into force on 9 November 2011.
The latest enlargement of the EU took place on 1 July 2013 when the Republic of Croatia joined the Union, and upon the entry into force of the corresponding EEA Enlargement Agreement, the EEA will comprise 31 countries with more than 500 million citizens. The EEA Enlargement Agreement is provisionally applicable as of 12 April 2014 and is currently pending ratification by the Parties.