(Uploaded by Plazi for the Bat Literature Project) During a long-term study on biodiversity of bats in the Yungas and Entre Rı´ os provinces, 1,304 specimens of bats included in the families Noctilionidae, Phyllostomidae, Vespertilionidae, and Molossidae were collected and checked for filarioids. Litomosoides molossi Esslinger, 1973 was recovered from the thoracic and abdominal cavities of Molossus molossus (prevalence [P] ¼ 6.4%); Litomosoides chandleri Esslinger, 1973 from Artibeus planirostris (P ¼ 6.9%), Sturnira oporaphilum (P ¼ 66.6%), Sturnira erythromos (P ¼ 23.8%), Sturnira lilium (P ¼ 7.2%), and Eumops perotis (P ¼ 50%); and Litomosoides saltensis n. sp. was collected from Eptesicus furinalis (P ¼ 1.7%). In this paper, we emend the description of L. molossi; describe a new species, Litomosoides saltensis n. sp., on the basis of 1 female specimen; and report for the first time L. molossi and L. chandleri parasitizing Argentinean bats, expanding the host and locality records. Litomosoides molossi exhibits a slender buccal capsule, with an anterior segment transparent, and the posterior chitinous portion displays 2 thickenings in the first third; possesses 1 dorsal prominent cephalic papilla and 4 labial papillae distributed around the mouth; cuticle with lateral punctuations all along the hypodermic chords in both sexes; and male with area rugosa and tail without cloacal papillae. In L. chandleri, the lateral punctuations are distributed on the posterior extremity of the body in both sexes. Litomosoides saltensis n. sp. displays a thick buccal capsule with a posterior segment well cuticularized, possessing 2 thickenings in the anterior half; 4 labial and 2 ventral cephalic papillae; a globular vulva located anterior to the esophagus–intestine junction; cuticle with lateral punctuations in the posterior extremity of the body; and tail with salient phasmids. We also provide a taxonomic key for the identification of the Litomosoides sp. of bat dwelling. Long-term studies and large sample sizes are needed to detect the presence of Litomosoides sp. in bats, in contrast to the findings in cricetid rodents, which seem to be more frequently collected.