We have been able to collect, in all, 43 reported cases of teratoma of the thyroid gland. Of these, 28 probably represent true examples of the condition, while the remaining 15, having been reported before the microscope came into general use, are more doubtful. The first case reported is certainly open to doubt. It is that of Grassi (1), who in 1691 described the removal of a completely developed fetus, the length of a finger, from a swelling in a woman's neck. On the other hand, the case described by Joube (2) in 1754 is quite probably a teratoma. In a tumor of an infant's neck so large that it caused dystocia, he found blood, bone, cartilage, and round hollow structures resembling loops of intestine. Similarly Morand (3) in 1766 found a tumor of the neck of a new-born infant which contained hair, a mass resembling a misshapen head, and another mass resembling loops of intestine. Aside from these cases, there are found in the earlier literature, according to Hunziker (4), who has made a thorough analysis of the subject and from whose article these references are taken, 8 other cases, as follows. In 1834 Bury (5) described a large, chiefly right-sided tumor of the neck of a new-born infant, containing skin and bone. In 1839 Mondini (6) reported a case of a large tumor of the base of the neck, replacing the thyroid and receiving its blood supply from the superior and inferior thyroid arteries. Adelmann (7) in 1842 described a tumor of the neck in a new-born infant which contained serous cysts and cartilage. Gilles (8) in 1852 published an account of a cystic tumor of the neck which contained bone covered by periosteum and teeth. Hess (9) in 1854 described a case which was studied forty years later by Wetzel (10), and called by him a teratoma of the thyroid. This is the earliest of the more definite eases. In 1868 Boucher (11) gave a gross and microscopic description of a teratoma of the thyroid. Tannahill (12) in 1871 mentioned a partly cystic, partly solid tumor larger than a child's head occupying the region of the thyroid. This tumor contained bone and cartilage and was called by him a myxosarcoma. Houel (13) in 1873 described a congenital tumor of the thyroid region as large as a child's head, gelatinous, cystic, and with large numbers of cartilaginous areas.