Differentiated thyroid carcinoma (DTC) is generally indolent in nature and, even though it metastasizes to distant organs, the prognosis is normally excellent. In contrast, the overall survival (OS) of patients with radioactive iodine (RAI)-refractory and progressive metastases is dire, because no effective therapies have been available to control the metastatic lesions. However, recently, administration of tyrosine-kinase inhibitors (TKIs) has become a new line of therapy for RAI-refractory and progressive metastases. Previous studies have reported significant improvement regarding the progression-free survival rates of patients with metastatic lesions. However, TKIs cause various severe adverse events (AEs) that damage patients' quality of life and can even be life-threatening. Additionally, metastatic lesions may progress significantly after stopping TKI therapy. Therefore, it is difficult to determine who is a candidate for TKI therapy, as well as how and when physicians start and stop the therapy. The present review, created by Committee of pharmacological therapy for thyroid cancer of the Japanese Society of Thyroid Surgery (JSTS) and the Japan Association of Endocrine Surgeons (JAES) describes how to appropriately use TKIs by describing what we do and do not know about treatment using TKIs.