The current level of knowledge about radioiodine therapy (RITh) for well-differentiated thyroid carcinoma under consideration of the recent literature is summarised. In RITh for thyroid carcinoma two major fields can be distinguished: the ablation of the thyroid remnant and the therapy of recurrences resp. local and distant metastases. New large American studies indicate, that the prophylactic post operative ablation of the thyroid remnant in primary tumours over 1.5 cm in diameter is linked with a distinct improvement of the long-term prognosis. The RITh is effective also in distant metastases, if applied early, when the tumour volume is still small. The prerequisite is an appropriate follow-up. Surveys about the application of RITh for well-differentiated thyroid carcinoma in Europe and in the USA reveal that uniform treatment recommendations designed to conform interdisciplinary demands are urgently required.