It is generally accepted that the Tg cut-point value in the TSH-suppressed state suggestive of disease-free survival in DTC patients after surgery and 131I nail clearing therapy is 1 ng/mL. However, the post-TSH-stimulated serum Tg cut-point value that predicts residual or recurrent DTC tumors is more controversial. The available evidence suggests that Tg>2ng/mL after TSH stimulation (TSH>30mU/L) may be a highly sensitive indicator of the presence of cancer cells, with a positive predictive value of almost 100% and a high negative predictive value. If the Tg cut-point value after TSH stimulation is reduced to 1ng/mL, the positive predictive value is about 85%; when it is reduced to 0.5ng/mL, the positive predictive value is further reduced, but the negative predictive value can be as high as 98%. In patients with DTC who have cleared all of their thyroid, the Tg cut-point value suggesting disease-free survival can be set at 1ng/mL for basal Tg (in TSH suppressed state); 2ng/mL for Tg after TSH stimulation (TSH>30mU/L).(Recommended level C)