Variation was assessed in the neotropical bat Phyllostomus discolor from a number of morphometric characters (length of one limb bone and eight cranial measurements). Sexual dimorphism is significant and is attributable to subtle differences in shape rather than to differences in size. Geographic variation among 13 samples of males and 8 samples of females indicated pronounced phenetic heterogeneity among populations within and west of the Andes Mountains, through Central America, and into southern Mexico. Populations east of the Andes Mountains are more homogeneous. Range disruption during the Pleistocene and past and present topographical hindrances to gene flow may be responsible in part for observed patterns of variation.