The article presents the results of archaeological study of Irganai settlement I of the Middle and early stage of the Late Bronze Age in the area of construction of Irganai hydroelectric station in 2005. A rectangular stone room has been revealed and delineated here. In the north-western part of the excavation site, a part of a stone wall has been identified, it runs westward and is perpendicular to the western wall of the oval room excavated in 2003-2004. It has been established that the western end of this wall is connected to the one revealed in 1988, i.e. actually it continues the latter. The length of stone wall 1 is 6.8 m, its height ranges from 1.7 to 1.9 m. The excavations have revealed one more wall (wall 2). It is connected to stone wall 1, is perpendicular to it and runs southward. Wall 2 is narrower than wall 1. Its length is 6.4 m, and the height of the preserved wall ranges from 0.8 to 1 m. A significant archaeological material has been found here: tools, weapons, ceramics, as well as considerable osteological material. Research of 2005 revealed a new interesting data for cultural and historic interpretation of the Bronze Age sites of the Irganai basin and the mountainous part of Dagestan. The materials from Irganai settlement I, revealed during excavations of 2005, date back to 18th - 14th centuries BC. Study of the materials from Irganai settlement I and Irganai burial I along with the materials from earlier excavations allow to establish Irganai local variant of the Ginchi-Gatynkali culture of early stage of the Bronze Age of Mountainous Dagestan and Southeast Chechnya.