Small mammal trapping showed that a minimum of 12 species live in and around Katavi National Park in western Tanzania. Species richness and abundance were greater outside the park than inside, extending results of an earlier study. Species richness and abundance were not significantly associated with vegetation cover or plant biomass but were negatively correlated with seed diversity, seed biomass, and possibly small carnivore abundance. Unfortunately, small mammal diets are unknown in this ecosystem and it can be argued that carnivores are unlikely to reduce species diversity, casting doubt on the importance of these variables. While the factors causing small mammals to fare poorly in this protected area are not yet understood, reduced food availability remains the best candidate.