ENThe article analyzes dialectological and sociolinguistic data collected from the border regions of Southeast Lithuania. The data are mostly bilingual and multilingual audio recordings of residents recorded over nearly five decades (1964–2013). Two variants of the Slavic languages — the Belarusian dialect and the local version of the Polish language — began to spread there from the 19th century, but until the end of the 20th century Southern Aukštaitian Dzūkian was spoken there as well. The work aims to analyze the features of live communication of the Southern Aukštaitians in the border areas where four languages were and still are used, to determine the types of code-switching and what functions code-switching performs in the language of representatives of the older and middle generations. In the 21st century, people of all generations in the region no longer associate themselves with any nation but identify themselves simply as “locals”. The repertoire of languages in the Šalčininkai district varies according to age. Older and middle-aged people are fluent and actively use several Slavic languages in relevant situations, namely the Belarusian dialect poprostu, the local Polish version język tutejszy, and the Russian language common in Soviet times. In addition to the languages listed, the younger generation also uses the general Lithuanian language, but their language skills differ from those of the older generations. During conversations, representatives of both generations easily exchange several languages. The vitality of several languages shows that multilingualism exists in the region at the ethnic level. Keywords: sociolinguistics, language contacts, Southeast Lithuania, Šalčininkai district, type of code-switching, function of code-switching. [From the publication]