Dermoid cyst of the mouth and submandibular area represent an unusual clinical entity. Dermoid cyst is a form of cystic teratoma, derived from epithelial debris or rest enclaved during the midline closure of the bilateral mandibular and hyoid branchial arches. Dermoids commence shortly after birth, but on account of their slow and painless growth, they attract little attention until their size gives annoyance. Recently, the authors had experienced a large dermoid cyst of the floor of the mouth.