The first information on species of bat flies and their hosts in the state of Mato Grosso do Sul is given. The specimens of bats and bat flies were collected in a transitional area of cerrado and semideciduous forest and in a deciduous forest. Seven species of streblid and one of nicteribiid flies were collected on five species of bats. All bat flies are recorded for the first time in Mato Grosso do Sul and Basilia bequaerti Guimarães & D´Andretta, 1956 is a new record for Brazil.
bat flies; ectoparasite; Phyllostomidae; Vespertilionidae
