Serum thyroglobulin (Tg) is a tumour marker used to manage patients with differentiated thyroid carcinoma (DTC). However, its diagnostic accuracy can be questioned when thyroglobulin antibodies (TgAb) are simultaneously present. Changes in serum TgAb can also serve as an index of disease progression in DTC. The objective of this study was to identify the relationship between TgAb titre and disease progression, defined as radiological or histological evidence of recurrence. Eighty patients with DTC were classified on the basis of TgAb (kIU/L) into undetectable (U<2.0) n=23; detectable (D<2.0<20.0) n=42 and elevated (E>20.0) n=15. These subdivisions were made possible by employment of a highly sensitive direct RIA for measurement of serum TgAb with serum Tg also measured by RIA (Reference range: T4 suppressed patients <2.0 ng/ml). Of the 80 patients, 24 (30%) had histological and radiological evidence of local or distant recurrence while 56 (70%) were disease free. Disease recurrence was observed in 15/42 patients with detectable (D) TgAb and in 7/15 with elevated (E) antibodies compared to 2/23 with TgAb (U) (P<0.001 and P<0.0001) respectively. In terms of predicting recurrence in DTC measurement of TgAb exhibited a greater sensitivity (91.7%) than serum Tg (66.7%). While neither serum Tg or TgAb alone can definitively predict the course of thyroid cancer, they indicate that the presence of TgAb, either detectable or elevated, carries its own prognostic significance in predicting recurrence in DTC.