Comparisons of the karyotypes of the species of Vampyressa suggest two modes of chromosomal rearrangements in the derivation of the Vampyressa karyotypes: pericentric inversions in V. brocki, V. nymphaea, and V. bidens; and translocations (fusions) in V. melissa and the variants of V. pusilla. This Vampyressa phylogenetic model was used to evaluate the possible derivations of the chromosomal patterns of the 97 species of phyllostomid bats whose karyotypes are known. Sufficient variation to indicate probable evolutionary patterns, in addition to that outlined for Vampyressa, was found at the species level for Micronycteris and Tonatia, and at the generic level for the Glossophaginae, Carolliinae, and Stenoderminae. The analysis supports the points of view presented herein that (1) the common (often considered the ancestral) 2n = 32, FN = 60 configuration was independently acquired by three or more evolutionary lineages and, therefore, must be considered to be derived; (2) the primitive phyllostomid karyotype had a high diploid number (near 40, but possibly as high as 46) and a low fundamental number (near minimum); (3) there was a general trend toward reduction in diploid numbers concomitant with maximization of fundamental numbers; and (4) totally biarmed autosomal configurations, which characterize the majority of the Phyllostomidae, are comparatively more stable than those karyotypes in which half or more of the autosomes are uniarmed. Fourteen karyotypes are reported here for the first time, including that of Vampyressa melissa, which has the lowest diploid number known in the Chiroptera (2n = 14).