Riga and Norrköping (Sweden) oficially became twin cities on November 16, 1988 with the cooperation agreement mutually signed in Norrköping.This agreement has been renewed and improved for several times, adding a detailed cooperation plan every year. In 1999 a wide seminar ‘Riga and Norrköping 1989–2009’ took place in Riga, marking the past 20 years of cooperation. In honour of this event the book ‘Riga un Norcepinga kopsoli. 1989 – 1999’ was published.Anniversary events dedicated to 20 years of cooperation and signing of the new Riga and Norrköping cooperation agreement took place in Riga on March 12, 2009.