The article concerns the issue - much debated in the recent years - of geographical location of the so-called Silesian tribes, mentioned in sources from the 9th to 11th centuries. The first issue considered is the definition of the word “tribe” in the context of studies of bygone Slavic societies; after deliberation the only possible definition was chosen – a “working” one, according to which every early medieval ethnic group which cannot be defined as a monarchy will be called a tribe. Furthermore, in the text the question was analyzed, whether the tribes known from the Henry IV’s document from the year 1086 (DH IV 390) were situated on the left bank of Odra river, or, as Sławomir Moździoch recently postulated, some of these tribes (Pobarane, Trebouane) were situated on the right bank. By incorporating in this discourse data originating from the Otto III's document from 995 (DO III 186) the issue was settled by deciding that all “Silesian tribes” known by their names were situated on the left bank of Odra.