Inventories of mammals in the Neotropics usually are derived from specimens recorded at a single site, about 25 km² in area, but this may not represent the diversity of the whole region. To illustrate this point, presence of 42 species of nonvolant mammals was recorded in the Chiquibul Forest Reserve, an area of subtropical wet forest in the Maya Mountains of western Belize. Data on diversity and abundance of mammals at that site were compared with 3 other sites in the Maya Mountains to determine how measurements varied with location of site. Of the nonvolant species, <33% were found at all 4 sites and >20% were found only at 1 site. Trapping success of researchers and densities of small mammals varied greatly between sites. Although number of species increased with research effort, the most extensively studied site did not encompass all mammalian diversity in the region. To obtain a representative mammalian inventory, effort should focus on sampling mammalian fauna at multiple sites, rather than increasing time at 1 site.