Abstract: DTC is the most common endocrine carcinoma and its routine treatment consists of total thyroidectomy and 131I thyroid remnant ablation.Currently,standard follow-up for DTC comprises Tg measurement and neck ultrasound as well as an additional radioiodine scan when indicated.As thyroid cells are assumed to be the only source of Tg in serum,circulating Tg serves as an excellent marker of persistent or recurrent disease in DTC follow-up.With the development of highly sensitive Tg assays,now it is possible to detect very low Tg concentrations which reflect minimal amounts of thyroid tissue without the need for TSH stimulation.This review is to introduce clinical implications of highly sensitive Tg assays.