The authors report on a case of a full-term infant with lumbar myelomeningocele who was found to have an intramedullary mass at the time of surgical repair of the defect. The intramedullary mass was consistent with a dermoid tumor both macroscopically and microscopically. This case provides evidence that dermoid tumors occurring at the site of previous surgical myelomeningocele repair are not always a consequence of incomplete excision of the dermal elements.