The abolition of police checks at common borders on 26 March 1995 included, along with the five original contracting parties of the 1985 Schengen Agreement (i.e. Germany, France, Belgium, the Netherlands, and Luxembourg), also Spain and Portugal.
Very soon, Italy (1990) and Greece (1992) acceded to the Schengen Implementing Convention; both countries, however, had to wait several years for full integration into the Schengen cooperation. Italy fully abolished police checks at its internal borders together with Austria in 1998, and Greece in 2000. A similar period of several years always separated the formal and practical accession to the Schengen area during all rounds of the Schengen enlargement process.
On 28 April 1995, Austria added its signature to the Schengen Implementing Convention and was followed by Denmark, Finland and Sweden on 19 December 1996. With respect to existence of the Nordic Passport Union, it was also necessary to solve consequences of this Schengen enlargement as Norway and Iceland were concerned; towards these countries standards of very close cooperation had been already applied for a number of years, including the removal of the obligation to present travel documents when crossing common borders.
The issue of Norway's and Iceland's integration to the Schengen cooperation was solved by means of a specific Accession Agreement, which resulted in the first enlargement of the Schengen area by non-EU countries. Police checks at borders with these five Nordic countries were removed in 2001 after it had been verified that all necessary conditions had been met.
On 21 December 2007, nine new EU Member States joined the Schengen area: the Czech Republic, Estonia, Latvia, Lithuania, Hungary, Malta, Poland, Slovakia and Slovenia.
On 12 December 2008 Switzerland became a new Schengen State.
Any other new Schengen states have to successfully pass the Schengen evaluation and demonstrate its readiness to fully apply the Schengen acquis and to abolish internal border control.
Currently, 4 states aim at joining Schengen.
Cyprus has already undergone one part of the evaluation, of which continuation is preconditioned by the fully operational second generation Schengen Information System (SIS II).
The start of evaluation of Liechtenstein´s preparedness for joining Schengen is preconditioned by entering into force of the protocol on its accession to the accession agreement between Switzerland and EU/EC. Currently, ratification process of this protocol is approaching its end.
The verification of readiness of Bulgaria and Rumania for accession into the Schengen area started in autumn 2008 and is under way. Both countries aim at joining the Schengen area in March 2011.