Member states

Find out when CERN's member states joined the organization.

• 29 September 1954

  Twelve founding members

• 1 June 1959

  Austria joins

• 1 January 1961

  Spain joins

• 29 September 1961

  Yugoslavia quits

• 31 December 1968

  Spain quits

• 1 January 1983

  Spain rejoins

• 1 January 1986

  Portugal joins

• 1 January 1991

  Finland joins

• 1 July 1991

  Poland joins

• 1 July 1992

  Hungary joins. So does the Czech and Slovak Federal Republic

• 31 December 1992

  The Czech and Slovak Federal Republic ceases to exist

• 1 July 1993

  The Czech Republic and the Slovak Republic join

• 11 June 1999

  Bulgaria joins

• 6 January 2014

  Israel joins

• 17 July 2016

  Romania joins