Reevaluation of the morphology of the crania, dentitions, and postcrania of the Eocene to Oligocene nimravines and Miocene barbourofelines confirms recent suggestions that each group is monophyletic. These two groups of catlike carnivorans possess synapomorphies in the cranium, mandible, dentition, and postcranium, and are referred to the Nimravidae. Diagnoses for the family and its two constituent subfamilies are emended. Cladistic analysis of the major clades within the Carnivora based on 40 characters taken mostly from the skeleton indicates that a sister-group relationship between the Nimravidae and the Aeluroidea has the greatest support. Nonetheless, evidence also exists for a close relationship between nimravines and caniforms, and for the view that nimravids are not most closely related to either of the major extant carnivoran clades. Relationships among many of the major carnivoran clades are supported by few well-corroborated characters. Many characters of potential importance for the resolution of carnivore relationships require more intensive study through character analysis.