(Uploaded by Plazi for the Bat Literature Project) The prevalence and intensity of arthropod ectoparasites collected from 90 specimens of Tadarida brasiliensis (Geoffroy Saint-Hilaire, 1824) captured in Concepción, VIII Región-Chile (36º40'S; 73º04'W) from November 2000 to March 2001 is presented. The ectoparasites collected were one species of flea, Sternopsylla distincta (Rothschild, 1903), and three species of mites, Chiroptonyssus robustipes (Ewing, 1925), Ewingana inaequalis (Ewing, 1938) and Notoedres lasionycteris (Boyd & Bernstein, 1950). The 100% of bats were parasited and 3,185 ectoparasites were collected. C. robustipes was the most common species with a 100% of prevalence. N. lasionycteris, E. inaequalis and S. distincta presented 40.0, 32.24 and 8.89% of prevalence respectively. The mean intensity of infestation was greater for C. robustipes with 34.25 mites/bats and in others species the intensity was a 2% lower. The prevalence and intensity of E. inaequalis and N. lasionycteris were significatively greater in males, while for S. distincta the prevalence was slightly greater only in females. The prevalence and intensity of some ectoparasites showed to be dependent on the host sex.