The studies were carried out during 33 years (1986-2019) in various types of agricultural ecosystems and shelter belts all over the territory of the Republic of Moldova. The aim of the study was to elucidate the demographic structure of the populations of Microtus arvalis and Microtus rossiaemeridionalis in the agrocenoses of the Republic of Moldova. Standard methods were used to assess the number of small mammals, to determine their reproductive status and fecundity, and to estimate the number of colonies. During the study, we captured 1070 individuals of Microtus arvalis and 530 of Microtus rossiaemeridionalis. Significant differences were established between the species M. arvalis and M. rossiaemeridionalis regarding the number of adult and juvenile males, reproductive and juvenile females in both peak and depression phases, as well as between the density of the studies species in various types of agrocenoses: perennial herbs, cereal fields and shelter belts. The gender ratio in vole populations on cereal crops and perennial herbs at different densities depends on the populational phase. In young individuals, the dispersal is more intense, they mature faster, reproduce better and have higher survival rate in comparison with resident individuals of the same age.