The social system in a free-living population of the mandarine vole Lasiopodomys mandarinus was examined in Selenginski District, Buryatia, by use of the mark-capture method. Mandarine voles lived in extended family groups. The members of the group occupied a common burrow and were strongly attached to it. The summer groups consisted of one breeding male, 1-5 breeding females, and young of 1-3 generations with a mean of 8.7 (range 3-22) individuals per burrow. Most of the offspring remained within the natal territory at least up to 50 days. None of the 72 young males and only three of the 73 young females became reproductive while staying in natal burrows. The change of sire appears to be the necessary condition for the reproductive activation of philopatric daughters. Thus, L. mandarinus exhibits a high level of sociality based on communal breeding, prolonged pair-bonding and parent-young relationships. This set of traits is also reported in the literature for Lasiopodomys brandti. It is suggested that sociality was characteristic of ancestral above ground form and represented the precondition to occupy the recent niche of the fossorial stenophage.