Fauna of small mammals (Rodentia, Insectivora) from middle and lower curse of Nistru river and its importance in maintenance of leptospirosis foci. The studies were performed in 2010-2016 in various ecosystems from middle and lower curse of Nistru river basin. In total 1407 small mammals from 16 species were registered. The highest diversity was registered in the middle sector of the river (northern zone of the rpublic). The most abundant and dominant in the studied ecosystems were the species of genus Apodemus. In the epizootic process are involved the species A.sylvaticus, A.flavicollis, A.agrarius, A.uralensis, M.minutus M. musculus and R.norvegicus and in the northern zone the process occurred more actively. In small mammal populations 47 specific antibodies for three leptospira serotypes were determined: L.icterohaemorrhagiae, L.pomona, L.canicola. The obtained data confirm the importance of rodent species as hosts for leptospira and its maintenance in the environment.