Upgrade of the definition of Schengen Countries (December 2013):

Today the Schengen Area consists of:

a) 22 of European Union Countries: Austria (Österreich), Belgium, Czech Republic, Denmark (Danmark), Estonia, Finland (Suomi), France, Germany (Deutschland), Greece (Ελλάδα), Holland (Nederland), Hungary (Magyarország), Italy, Latvia, Lithuania (Lietuva), Luxembourg, Malta, Poland (Polska), Portugal, Slovakia, Slovenia, Spain (Espana), Sweden (Sverige),

b) 4 countries situated outside of the European Union Zone: Norway, Iceland, Switzerland, Liechtenstein,

c) 3 special countries - cities: Vatican, San Marino and Monaco.

There are a few countries which are eager to join the Schengen Zone.
The candidates to become next members of the Schengen Countries Group are: Bulgaria, Romania, Cyprus and Croatia.