Whereas scintigraphy and ultrasonography are the primary imaging modalities used for the investigation of thyroid disorders, MR imaging is generally used for specific indications, including evaluating the extent of substernal goiters, assessing the effect on adjacent structures, imaging the local extent of thyroid carcinomas, and localizing recurrent sites of thyroid neoplasia. MR imaging also has been used for the investigation of congenital disorders of the thyroid gland and the evaluation of diffuse thyroid disease, such as Grave's disease, Hashimoto's and Riedel thyroiditis, and hemochromatosis. MR imaging of the parathyroid glands is generally used for patients with recurrent or persistent hyperparathyroidism following neck exploration. MR imaging provides useful information about morphologic abnormalities of the thyroid and parathyroid glands. MR imaging has good sensitivity and positive predictive value for the identification of non-ectopic and ectopic abnormal parathyroid glands. The detailed anatomic information provided by MR imaging is useful in planning a surgical approach and is complementary to other imaging methods used in the investigation of recurrent or persistent hyperparathyroidism.