The thyroglossal duct cyst is the most common congenital neck mass, resulting from persistence and dilatation of remnants of an epithelial tract formed during migration of the thyroid during embryogenesis. Approximately 7% of the population has thyroglossal duct remnants. Although thyroglossal duct cysts generally present clinically in children, it is important to understand that the lesion can present in adults as well, sometimes much later in life. Incidental carcinoma of the thyroglossal duct cyst is rare, but is more likely to occur in adults than children. Between 1991 and 1998, 11 cases of thyroglossal duct cysts were seen in adult patients at Georgetown University Medical Center, including 2 cases containing papillary carcinoma. This report discusses their clinical presentations and management.