The following contribution will present the changes of the border between Slovenia and Croatia in 1956. We will focus on the territory of the cadastral municipalities of Pregara, Gradin, and a part of the Topolovec cadastral municipality. Towards the end of the war the majority of the population allegedly opted for annexation to Slovenia. However, in 1947 when this territory went to Yugoslavia in accordance with the peace treaty, these towns were annexed to the Buzet district or to the People's Republic of Croatia. In June 1955 the majority of the population expressed a wish to be included in the People's Republic of Slovenia, and therefore the Slovenian government proposed to the government of Croatia that the border be changed. The republican governments reached an agreement, which was then carried out in accordance with the constitutional principles, as set out by the Yugoslav Constitution. First the agreement was confirmed by the Assemblies of both republics, Croatia and Slovenia, while in March 1956 the ordinance on the alteration of the borders between the republics was also confirmed by the Federal People's Republic. This was the only example of an alteration of the Slovenian-Croatian border that was confirmed in the manner as prescribed by the Constitution, while the questions involving the other disputed border sections remained unsolved until the Slovenian and Croatian attainment of independence