The article provides an overview of archaeological study of Vetluga region territory, including the history of the field research, key scientific works focusing on materials from the studied medieval sites, as well as scientific hypotheses built on these sources. Studies of the Mari archaeological expedition over 60 years of its existence formed the core of the archaeological artifacts, mainly associated with the issue of formation and development of the medieval Mari culture. New stage in the study of medieval antiquities of the Vetluga region began in late 20^th – early 21^st centuries. Materials yielded by new expeditions, led by the author, have not yet been fully offered for scientific discussion. This article presents some preliminary results of the new studies on the early medieval sites (Chortovo hillfort, Vyzhum, Rusenikha and “Kuzinskie khutora” cemeteries), which provided substantial evidence for further studies into the ethnic genesis and cultural connections of the early Mari.