The genus Myotis is of interest to the evolutionist because of its diversity and because of its nearly cosmopolitan distribution. An understanding of the biology of this remarkable genus may provide insight into its success, as well as the success of other expansive groups of mammals. As part of an overall study of Myotis, I subjected measurements of 48 morphological traits from most of the described species to standard numerical taxonomic analysis. I hoped to delineate phenetic groupings in the genus, and to learn if these groupings provide insight into adaptive diversification of species, into the history of the genus, and into a replicable approach to its classification. Phenograms based on Pearson product-moment correlation coefficients and on coefficients of taxonomic distance were prepared, as was a three dimensional model depicting phenetic placement of the species with respect to the first three principal factors derived from a centroid factor analysis. The analysis was performed using the Numerical Taxonomy System of Multivariate Statistical Programs (NT-SYS) developed by F. James Rohlf, John Kishpaugh, and Ron Bartcher, at the University of Kansas in 1968. For methodology, see especially Sokal & Sneath, 1963, and Rohlf, 1968.