The volume of Vilnius guild documents - written down from the end of the 15th century until the mid-18th century - published in 2006, is a good source for historical as well as linguistic (also onomastic) studies. It comprises remarkably valuable anthroponymic material which includes approximately one and a half thousand surnames of different origin - Slavic (mainly Polish and Belorussian) and non-Slavic (mainly German and Scandinavian, less frequently Lithuanian). It certifies the early period of the formation and functioning of a burgher's surname in Vilnius and, simultaneously, verifies some opinions on a typical character of the structure of a burgher's surname. It can be observed that surnames with the formative -owicz, -ewicz were the most popular among Vilnius burghers. Besides, a very early introduction of surnames with the formative -cki, -ski, originally typical of the nobility, can be also noticed. Furthermore, the anthroponymic material is a proof of complex ethnic relations showing that the Vilnius burghership constituted a multiethnic group which consisted of Polish, Russian, Lithuanian, German, Scandinavian and Jewish population as well as of representatives of a number of other nations.