Before World War II, 97% of the population declared itself Roman Catholic, around 2.5% as Lutheran, and around 0.5% of residents identified themselves as members of other denominations. Catholicism was an important feature of both social and political life in pre-Communist Slovenia. After 1945, the country underwent a process of gradual but steady secularization. After a decade of severe persecution of religions, the Communist regime adopted a policy of relative tolerance towards the churches, but limited their social functioning. After 1990, the Roman Catholic Church regained some of its former influence, but Slovenia remains a largely secularized society. According to the 2002 census, 57.8% of the population is Roman Catholic. As elsewhere in Europe, affiliation with Roman Catholicism is dropping: in 1991, 71.6% were self-declared Catholics, which means a drop of more than 1% annually. The vast majority of Slovenian Catholics belong to the Latin Rite. A small number of Greek Catholics live in the White Carniola region.
Despite a relatively small number of Protestants (less than 1% in 2002), the Protestant legacy is important because of its historical significance, given that the Slovene standard language and Slovene literature were established by the Protestant Reformation in the 16th century. Nowadays, a significant Lutheran minority lives in the easternmost region of Prekmurje, where they represent around a fifth of the population and are headed by a bishop with the seat in Murska Sobota.
Besides these two Christian denominations, a small Jewish community has also been historically present. Despite the losses suffered during the Holocaust, Judaism still numbers a few hundred adherents, mostly living in Ljubljana, site of the sole remaining active synagogue in the country.
According to the 2002 census, Islam is the second largest religious denomination with around 2.4% of the population. Most Slovenian Muslims came from Bosnia, Kosovo, and