Dermoid cyst of the floor of the mouth is infrequent and of congenital origin as a dysontogentic. Cysts of the floor of the mouth has been classified as epidermoid, dermoid and teratoid eyst. Dermoid cyst is more common in young adults in the second or third decades, and there is no sex predilection. The authors have recently experienced a case of huge dermoid cyst in the floor of the mouth. Surgically the cyst was completely removed with blunt finger dissection under the general anesthesia, and it was a yellowish-red coloured large egg-sized mass which contained fetid odor cheesy material. Histopathologically the final diagnosis was confirmed as dermoid cyst.