Patterns of dental microwear provide some of the best indirect evidence of tooth use and diet in living and extinct species, and thus can supplement inferences based on gross morphology. In this paper, dental microwear features are examined in the extinct sabretooth cat Smilodon fatalis and among eight species of extant large carnivores, including felids, canids, hyaenids and a mustelid. Although all the living species are primarily carnivorous, some differ in the relative quantities of large bones consumed; hyaenas are the most frequent bone-crushers and cheetahs the least. Because bone is harder than meat, interspecific differences in bone consumption are expected to be reflected by differences in microwear pattern. Scanning electron micrographs of the wear facet of the lower first molar (carnassial) were used to estimate the average density, size, shape and orientation of microwear features for each species. Results indicate that dietary differences are highlighted when features shorter than 30 μm in length are excluded from the analysis. When this is done, hyaenas are distinguished from other species by a combination of relatively few long features and a high proportion of pits to scratches. By contrast, the cheetah is characterized by a predominance of narrow features, relatively few of which are pits. Species of intermediate diet, such as the wolf, leopard, wild dog and wolverine, tend to be intermediate in pit density and feature shape. Comparisons of the carnivore microwear data with that published for primates reveal that the eight carnivores are most similar to frugivorous primates that specialize on relatively hard fruits. In addition, the orientation of microwear features is significantly more variable in carnivores than in the only comparably studied primate, the chimpanzee. This suggests that many of the microwear features on the carnassial are produced by food moving in directions other than occlusal pathways. The pattern of microwear features in the sabretooth cat is distinct from all of the sampled extant carnivores. Smilodon has relatively narrow, long features and an extremely low pit frequency. Thus Smilodon probably consumed less bone than does the cheetah and may have left behind significant amounts of bone and meat for scavengers. The sabretooth cat may have avoided bone in order to protect its long canines from breakage.