The extradosed bridge can be thought of as intermediate between the girder and cable-stayed bridge forms. This paper explores the boundaries of this form of bridge to attempt to define them more clearly. The paper summarises previous work on extradosed bridges and outlines the authors' own findings from their parametric study of a bridge near the boundary between cable-stayed and extradosed. The key parameters of extradosed bridges are outlined and compared with those for girder and cable-stayed bridges. The study indicates that although there is a clear division between girder and extradosed bridges the boundary, if any, between extradosed and cable-stayed forms is less clear.