The presence of an ovarian dermoid cyst in the pelvis may be suspected or confidently diagnosed by the recognition of one or more of the following appearances:— 1. Tooth formation—which may be associated with limited ossification. Individual dental structures may be seen as unformed denticles or as fully-developed teeth: whilst a single tooth may be recognised it is commoner to see groups of dental structures. It is as well when more than one tooth is seen in the pelvis in an antero-posterior view to take oblique radiographs: in this way it may be possible to dissociate two groups of dental structures and show that two dermoid cysts are present.