The diversity of species (56) of North American mice within the genus Peromyscus reflects the wide range of habitats they occupy and corresponding variation in behavior and morphology. We studied differences in climbing behavior and anatomy among three populations of mice ( P. maniculatus gracilis, P. m. bairdii, and P. leucopus noveboracensis) that can be found in the same general geographic area, but tend to use different habitats that vary in tree cover. Laboratory trials revealed statistically significant differences among populations in tendency and ability to climb on both horizontal and vertical rods. Differences in tail length were found among the populations, but tail length by itself did not predict differences in climbing behavior. Other morphological differences among the populations appear to be at least equally important in explaining differences in climbing behavior.