Keys and ancillary information are provided to summarize understanding of the diversity of bats (Mammalia: Chiroptera) in East Africa. We reviewed literature and online databases to aid identification of 145 species of bats known to inhabit Kenya, Tanzania, Burundi, Rwanda, and Uganda. National tallies of species were as follows: Kenya, 108; Tanzania, 105; Uganda, 98; Rwanda, 49; and Burundi, 33. Kenya, Tanzania, and Uganda harbor three of Africa's four richest known bat faunas, but all are incompletely known. Ordination analysis via multidimensional scaling suggests that the East African bat fauna shares elements with those in North Africa, West Africa, and South Africa. We constructed keys to species, drawing from the literature and modifying or expanding them to suit the East African bat fauna. Insofar as possible, we used characters that are visible externally or through cursory cranial or dental inspection. The keys are organized taxonomically: an initial key to the 10 families of bats in East Africa directs the user to separate keys for each family and, in the case of Molossidae and Vespertilionidae, to separate keys for the more diverse genera. Each key is flanked by a brief introduction, a measurement table containing the ranges of various external and cranial measurements (in some cases augmented by salient diagnostic characters), and individual species accounts. The latter contain scientific and common names, type locality and description, geographic range, and current conservation status as determined by IUCN in 2011. Species of certain vespertilionids are too subtly distinguished and/or incompletely documented to be identified with our keys; additional studies of tragus size and shape, bacular morphology, and call notes will be needed to resolve these species. We conclude with accounts for species that we excluded from the East African fauna (with our rationales) and a list of species that may eventually be added to the East African fauna.