Two cases of hydatid cyst of the thyroid are reported and the rare cases in the literature reviewed. Hydatidosis located in the thyroid is an infrequent finding, even in endemic countries. Finding on clinical examination are usually those of a cold thyroid nodule, and diagnosis is by detection of other sites for the lesion, positive results of immunologic tests, or often only after histology of an operative specimen. The spontaneous course of the affection may be interrupted by complications due either to the size of the lesion or the parasite itself. Treatment is surgical, usually by a hemithyroidectomy.