Body size is an important measure in biology and especially in paleobiology. With respect to fossil penguins from the Eocene La Meseta Formation of Seymour Island (West Antarctica) the overall size has to be judged from the dimensions of single bones. The analysis based on selected measurements of hind limb bones from the Polish collection of Eocene Ant­arctic penguins yielded results supporting predictions published formerly. Estimated body masses and lengths indicate that mean interspecific body size of extinct Antarctic Spheniscidae exceeded that of Recent species.