The anatomy of the cavum tympanicum (middle ear region) and os quadratum (quadrate) is described for the Cariamiformes. Specimens from both extant species are included. Pathways of blood vessels and nerves and their foramina are described as are other important anatomical characters. More research at both the morphological and molecular levels is needed to fully understand where to place this order within birds. An understanding of the anatomy of middle ear structures will be important to taxonomists who are looking for characters on which to test their hypotheses of relationships.