ENThe article addresses two main issues. The first concerns the reconstruction of the distribution boundaries of archaeological sites associated with the Smolensk-Polack Long Barrow Culture and the East Lithuanian Barrow Culture in the interfluve of the Western Dvina (Daugava) and Neman during the last centuries of the first millennium AD (9th–10th centuries, up until the early 11th century). The second issue explores the nature of relations among the population of this frontier: whether these relations can be characterised as peaceful coexistence or as conflict involving different groups of frontier dwellers competing over territory and resources. Both issues are examined based on archaeological evidence. Keywords: archaeology of the borderland, Krivichs, Lithuanians, Smolensk-Polack Long Barrow Culture, East Lithuanian Barrow Culture.