The locomotor behaviour of some large extinct carnivores, including several species of Plio-Pleistocene sabre-tooth cats, is here reconstructed, based on a comparison of the cross-sectional geometric properties and linear dimensions of their femora and humeri with those of large modern carnivores. The long bones are modelled as simple beams, thereby allowing the use of basic beam theory in assessing relevant functional parameters such as second moments of area of the diaphyses when subjected to compressive and bending stresses. Three Pleistocene carnivores, Smilodon fatalis, Homotherium serum, and Panthera atrox seem to have had ecological and functional equivalents among the late Miocene-Early Pliocene genera, Barbourofelis, Machairodus, and Nimravides, respectively. Barbourofelis and Smilodon were ‘cat-like’in dental morphology but some structural characteristics of their limb bones had ‘bear-like’affinities. Machairodus and Homotherium were cursorial, whereas Nimravides and P. atrox display the limb morphology of true ambush predators. Various aspects of the postcranial skeleton of some of these extinct carnivores suggest that they may have employed locomotory gaits that lack modern analogs.