Abstract:We add new localities to the distribution of bats of the families Molossidae and Vespertilionidae in southern Argentina. We report the southernmost known record for any bat species of the family Molossidae in the world, which corresponds to a locality in the Argentine province of Santa Cruz, for Tadarida brasiliensis . Also, new records of this species are added to the provinces of Chubut and R í o Negro. Additionally, we provide new localities that extend the distribution of some species of Vespertilionidae, by adding Histiotus magellanicus and Lasiurus varius to Chubut, and new records for Histiotus montanus to Santa Cruz and for Myotis chiloensis to Chubut and Tierra del Fuego.