Allometric relationships are important sources of information for many types of anthropological and biological research. The baseline for all allometric relationships is isometry (or geometric similarity), the principal that shape is invariant of size. Here, we formally test for geometric similarity in modern humans, looking at the maximum lengths of four long bones (humerus, radius, femur, and tibia). We use Jolicoeur's multivariate allometry method to examine globally distributed samples of human populations, both collectively and individually. Results indicate that humans are not geometrically similar, although morphological deviations from isometry are small. Am J Phys Anthropol, 2008. © 2008 Wiley-Liss, Inc.