The karyotypes of 10 Taiwanese vespertilionid bats were examined for the 1st time. Three Myotis species (M. formosus watasei, M. latriostris, and M. taiwanensis) have the standard Myotis karyotype of 2n = 44 with FN = 50. The karyotypes of Plecotus taivanus (2n = 32, FN = 50), Eptesicus serotinus horikawai (2n = 50, FN = 48), Arielulus torquatus (2n = 50, FN = 48), and Murina puta (2n = 44, FN = 50) show conservative patterns when compared to other species of the same respective genus. Scotophilus kuhlii (2n = 36, FN = 48) and Miniopterus schreibersii (2n = 46, FN = 50) have karyotypes essentially identical to those previously reported from other regions. Nyctalus sp. from Taiwan has the same karyotype of 2n = 36 as that of N. velutinus from China and should be separated from N. noctula (2n = 42) based on the different karyotypes.
