The calcanea of 20 species (7 genera) of members of the Mustelinae are described and compared. All species have a well-developed trochlear process and sustentaculum. The anterior articular surface is absent in 14 of the 20 species (all Mustela and most Martes). The genera Martes and Mustela are much alike except for size. Galictis is the most aberrant, approached most closely by Poecilictis. Poecilogale is close lo Mustela: Eira and Gulo close to Martes.